EP2987204B1

EP2987204B1 - Indicator device for machines and/or plants

Info

Publication number: EP2987204B1
Application number: EP15724024.3A
Authority: EP
Inventors: Marco Pizzato; Simone Zonta
Original assignee: Pizzato Elettrica SRL
Current assignee: Pizzato Elettrica SRL
Priority date: 2014-04-07
Filing date: 2015-04-07
Publication date: 2017-09-13
Anticipated expiration: 2035-04-07
Also published as: CN105408943A; WO2015155675A1; EP2987204A1; CN105408943B

Description

Field of the Invention

The present invention generally finds application in the field of electric indicating devices and particularly relates to an indicator device for machines and/or systems, preferably designed for application to switch and/or push button panels.

Background art

Electric indicating devices are known to be used in civil and industrial systems to indicate the state of an electric circuit associated with a machine, a system, an electric load or similar equipment.
Namely, common types of electric indicators include warning lights and sound alarms adapted for installation on panels of a switchboard or a push button box for an operator to monitor the state of the circuit or system.
These indicators generally comprise a hollow casing having a portion that projects out of the panel and accommodates therein one or more light sources for emitting a light radiation having a predetermined wavelength.
For space and power consumption saving purposes, LED sources are often used, which are mounted to a printed circuit board located within the casing, and having conductive tracks connected to the electric clamps of the device.
These allow the device to be removably connected to the terminals external electric circuit and may be actually designed as clamps or as clamping screws designed to be tightened into a corresponding threaded nut.
Nevertheless, these arrangements involve some complexity as they always require the action of an operator during connection of the printed circuit board to the clamps.
Such electric connection is always required to be manually established by a conductor with ends soldered to the printed circuit board and the clamps respectively.
Also, the action of an operator during assembly of the device considerably increases manufacturing times and costs.
In an attempt to obviate the above drawbacks, indicator devices have been developed, which have clamps designed to establish an electric contact with conductive areas directly formed on the printed circuit board with no intermediate connection element intervening therebetween.
KR1020120117102 discloses a light-emitting indicator having a box-like casing which houses a printed circuit board, the latter being designed to removably support a LED diode and having a conductive pad at both faces, for direct interaction with the screw or nut of the clamp.
While the configuration of the pads on the printed circuit board somewhat reduces the complexity of the device, it still has some recognized drawbacks.
The printed circuit board is interposed between the large head of the clamping screw and the threaded nut, which means that a stable electric contact between the pads and the respective terminals of the external circuit can only be established by tightening the screw into the nut with a non-negligible torque.
Therefore, the opposite faces of the printed circuit board are under a considerable pressure, which may cause the insulating medium of the circuit to break, especially if the operator inadvertently tightens the clamp with an excessive torque.
A further drawback of this arrangement is that the clamping screw and the nut are individual parts and must be manually fitted on the opposite faces of the printed circuit board.
The steps of positioning and later tightening the screw into the nut must be carried out manually, and this considerably increases the manufacturing times required for the device.
Furthermore, when the screw has to be tightened again into the nut after being completely loosened therefrom, the shank of the screw must be aligned with the hole of the nut, and this may be a very complex operation, especially when the operator is required to install the device in narrow or difficultly reachable spaces.

AMENDED DESCRIPTION (CLEAN)

Another serious drawback of this arrangement is the high risk that the nut will separate from the face of the printed circuit board during handling of the device. In this case, if this part is lost, the operator may be prevented from providing electric connection between the pad and the terminals of the external circuit, and the installation times may be extended.
KR 2012 0117102 A discloses a an indicator device having all the features mentioned in the preamble of claim 1. This know device has a circuit board that extends in a plane that is parallel to the longitudinal axis and that has a considerable longitudinal extension and additionally is relatively cumbersome to remove and/or replace.

Disclosure of the invention

The object of the present invention, as disclosed in claim 1, is to obviate the above drawbacks, by providing an indicator device that is highly efficient and relatively cost-effective.
A particular object of the present invention is to provide an indicator device that allows the printed circuit board to be protected from any inadvertent action by a user during connection thereof to the terminals of the system.
A further object of the present invention is to provide an indicator device that can be fully automatically assembled without requiring any manual action by an operator.
A further object of the present invention is to provide an indicator device that can be easily manufactured and has very short manufacturing times and low manufacturing costs.
A further object of the present invention is to provide an indicator device that has high strength and affords easy and quick connection of the system terminals in poorly accessible installation environments.
Yet another object of the present invention is to provide an indicator device whose printed circuit board is easily removable for maintenance.
Another important object of the present invention is to provide an indicator device in which parts cannot be lost during handling by an operator.
These and other objects, as better explained hereinafter, are fulfilled by an indicator device for an electric system or the like, which is designed to be secured to the panel of a switchboard and/or a push button box, as claimed in claim 1.
Advantageous embodiments of the invention are obtained in accordance with the dependent claims.

Brief Description of the Drawings

Further characteristics and advantages of the invention will become more apparent upon reading of the detailed description of a few preferred, non-exclusive embodiments of an indicator device of the invention, which are described as non-limiting examples with the help with the accompanying drawings in which:

FIG. 1 is a perspective view of an indicator device of the invention according to a first configuration while it is being secured to a panel of a switchboard and/or a push button box.
FIG. 2 is a side view of the device of Fig. 1;
FIGS. 3 and 4 are top and bottom exploded perspective views respectively of the device of Fig. 1 according to a first embodiment;
FIG. 5 is a lateral broken-away view of the device of Fig. 1;
FIG. 6 is a bottom view of the device of FIG. 1;
FIGS. 7 and 8 are top and bottom exploded perspective views respectively of the device of Fig. 1 according to a second embodiment;
FIG. 9 is a lateral broken-away view of the device of Figs. 7 and 8;
FIG. 10 is a lateral broken-away view of the device of Figs. 7 and 8 while an electric terminal of a system is being retained;
FIG. 11 is an enlarged lateral view of a detail of Fig. 10;
FIG. 12 is a lateral broken-away view of the device of Figs. 7 and 8 while an electric terminal of a system is being removed;
FIG. 13 is an enlarged lateral view of a detail of Fig. 12;
FIGS. 14 and 15 are lateral and broken-away lateral views respectively of an indicator device of the invention according to a third embodiment;
FIG. 16 is an exploded bottom perspective view of the device of Fig. 14.

Detailed description of a preferred embodiment

The above figures show an indicator device, generally designated by numeral 1, which is designed to be connected to a pair of terminals E of an electric system I.
Namely, the electric system I may be associated with a machine, a safety circuit, an electric load or similar equipment.
As schematically shown in FIG. 1, the indicator device 1 may be designed to be secured to the front wall F of a panel P of a switchboard, not shown, located near the machine.
Alternatively, the indicator device may be designed to be connected to a panel P of a push button box, not shown, which is either fixedly anchored to the machine or transportable by an operator.
In its basic configuration, the indicator device 1 of the invention comprises a casing 2 made of a first insulating base material.
The casing 2 defines a longitudinal axis L and houses therein a substantially flat, sheet-like electronic board 3, with a top face 4 and a bottom face 5.
The board 3, which is known per se, comprises a sheet 6 made of a second insulating base material, e.g. selected from the group comprising possibly composite epoxy resins, such as fiberglass, having a maximum compression strength C_max, of a predetermined value, e.g. about 5000 MPa.
The board 3 may comprise an electronic circuit 7, for example formed on the top face 4, which is connected to a pair of pads 8 formed on the bottom face 5 of the board 3, and has a light source 9, preferably a LED source, installed thereon in a substantially central position, and having electric contacts 10 connected to the electronic circuit 7.
The electronic circuit 7 may comprise two or more rectifier diodes 11 for allowing proper power supply to the source 9 when a DC or AC voltage V_al is applied to the pads 8.
In the configuration of the invention as shown in FIGS. 1 to 13, the electronic board 3 has a substantially circular plan shape, and in the configuration as shown in FIGS. 14 to 16, the electronic board 3 has a substantially rectangular plan shape
In both configurations, the board 3 is mounted in the casing 2 such that its main plane of extension X extends perpendicular to the longitudinal axis L.
Thus, the light radiation R emitted from the light source will mainly propagate in the longitudinal direction L, with the maximum light intensity and with no reflection on the inner surface 12 of the casing 2.
The device 1 further comprises electric connection means 13, which are adapted to electrically connect the pads 8 with the terminals E of the system I for power supply to the electronic circuit 7 and the light source 9.
In a peculiar aspect of the invention, the casing 2 comprises a body 14 which is adapted to be secured to a panel P and a bottom member 15 with a pair of seats 16 for the connection means 13, the latter comprising pressure elements 17 adapted to apply a stress S on the pads 8, which is lower than the maximum compression strength C_max of the second material of the board 3.
This will protect the sheet 6 of the board 3 against any excessive stress applied by an operator for connection of the pads 8 with the respective terminals E of the system I.
If the board 3 is made of a fiberglass sheet having a thickness of about 1.6 mm. the pressure exerted thereon by the pressure elements 17 must be considerably lower than the C_max value of 5000 MPa, which is deemed to be the maximum admitted value to prevent failure of the board 3.
Particularly, the bottom member 15 has a substantially transverse bottom wall 18 with a pair of passages 19 in communication with the seats 16 for allowing access to the connection means 13 by an operator.
In the configuration of the device 1 as shown in FIGS. 1 to 13, the body 14 of the casing 2 may have a substantially tubular shape and be adapted to be fitted into a through hole A of the panel P.
The body 14 may be stably secured to the panel P by means of an internally threaded annular ring nut 20 which is designed to be tightened onto external threads 21 formed on the side surface 22 of the body 14.
As best shown in FIGS. 2, 3, 4, 7 and 8, the body 14 may have a top end edge 23 which is designed to project out of the panel P and be coupled with a dome 24 made of a clear material, allowing the passage of the light radiation R emitted from the light source 9.
The top end edge 23 has a seat 25 for a ring 26 made of a polymeric material, which is designed to provide a seal against the inner surface 27 of the dome 24 and protect the device 1 from the ingress of dust and moisture.
The side surface 22 of the body 14 is connected to the top end edge 23 through an annular portion 28, which is designed to allow centering of the body 14 relative to the hole A of the panel P.
The body 14 may further have a downwardly open bottom end 19 whose inside diameter φ₁ is greater than the outside diameter φ₂ of the board 3, for the latter to be fitted into the casing 2 from the bottom.
The bottom end 29 of the body 14 has an end edge 30 with a pair of diametrically opposed openings 31, communicating with the seats 16 for the terminals E to be inserted/removed along a transverse plane X' and to be retained/released relative to the pads 8 of the board 3.
In the embodiment as shown in FIGS. 3 to 6, the pressure elements 17 may comprise a pair of screws 32 located in the seats 16 and adapted to be introduced into respective through holes 33 formed in the board 3 in correspondence of the pairs of pads 8.
Each screw 32 may be tightened into a corresponding blind hole 34, as best shown in FIG. 5, which is formed in the casing 2 in alignment with the corresponding through hole 33 of the board 3.
Namely, as clearly shown in FIGS. 3 to 5, the screws 32 may be of self-tapping type, with sharp external threads 35, and the blind holes 34 may initially have a substantially cylindrical inner wall 36, which is designed to be deformed as their respective screws 32 are first tightened therein, thereby forming internal threads, not shown.
Conveniently, the screws 32 will have an expanded head 37, with a diameter φ₃ greater than the diameter φ₄ of the passage 19 formed on the bottom wall 18 of the bottom member 15 to prevent it from coming out of the seat 16 when the device 1 is in a vertical position.
Furthermore, the large head 37 will be adapted to apply a predetermined pressure on the pads 8 to clamp the terminals E of the system I.
Thus, as the screw 32 is tightened/loosened, the terminals E will be retained or released against/from the pads 8 to supply or cut off power to the light source 9.
According to the invention, the first base material of the casing 2 is selected to have a maximum tensile strength T_max lower than the maximum compression strength C_max of the base material of the board 3.
Thus, the stress applied on the board 3 as the screws 32 are being tightened will never exceed the tensile strength T_max of the polymeric material at the inner wall 36, as the load will cause stripping of the threads formed in the blind holes 34.
As a non-limiting example, the base material of the casing may be selected from the group of plastic materials comprising PTFE, ABS, PP, PE, having a maximum tensile strength ranging from 1700 to 3500 MPa.
FIGS. 7 to 13 show a variant of the indicator device 1, which basically differs from the one as shown in FIGS. 1 to 6 in the shape and type of the pressure elements 17 and in the shape of the bottom member 15.
Namely, the pressure elements 17 comprise at least one pair of metal sheet elements 38, which are inserted in the seats 16 of the bottom member 15, and are acted upon by respective locking elements 39 housed in the seats 16.
Each of the sheet elements 38 preferably consists of a base metal sheet as thick as a few tenths, which is sheared and bent to have a substantially rectangular plan shape, with an upper end portion 40 and a lower end portion 41 inclined to form together an acute angle α of about 10-20°.
The upper end portion 40 is designed to compress or release the terminals E, and the lower end portion 41 is designed to interact with a respective locking element 39.
In the intermediate portion 42 between the upper end portion 40 and the lower end portion 41 have, an appropriately shaped appendix 43 is provided, which is substantially perpendicular to both end portions 40, 41 and is obtained by shearing and lifting a central portion of the base metal sheet.
Each of the locking elements 39 comprises a substantially cylindrical head 44 with a pair of wings 45 extending therefrom, each having a radially outward end rim 46 and being adapted to interact with the bottom end portion 41 of a corresponding sheet element 38 to force the upper end portion 40 against one of the terminals E.
Each seat 16 has a substantially cylindrical inner surface 47 with an inner diameter φ₅ that is greater than or equal to the diameter φ₆ of the head 44, which has an annular radially inward projection 48.
The latter is designed to interact with the inner rims 46 of the wings 45 to lock its respective locking element 39 in a lowered position in which the head 44 is substantially flush with the bottom surface 49 of the bottom member 15.
Furthermore, the bottom member 15 has a transverse wall 50 which delimits the seats 16 by its bottom surface 51 and the housing areas 53 for the terminals E, communicating with the passages 19, by its top surface 52.
The transverse wall 50 has a pair of first 54 and second 55 slits formed at diametrically opposite positions, facing the seats 16, the former being designed for the passage of the upper end portion 40 of a respective sheet element 38, and the latter being designed to retain its respective appendix 43 to form a fulcrum 56.
The sheet element 38 may pivot about the fulcrum 56 between two positions, which are inclined to a vertical plane π that passes through the longitudinal axis L.
At first, each locking element 39 is in its lowered position, i.e. flush with the bottom surface 49 of the bottom member 15, as shown in FIGS. 9, 10 and 11, and with the rims 46 of the wings 45 resting on the annular projection 48. In this position, the top of wing 45 abuts the lower end portion 41 of the sheet element 38 and causes it to form an angle β with the vertical plane π while maintaining the upper end portion 40 rotated upwards.
In this state, the terminal E may be slidably horizontally forced into the connection area 53 through a respective opening 31, thereby pushing the upper end portion 40, which will elastically hold it against removal.
When the terminal E has to be released for removal thereof from the connection area 53, the head 44 may be pressed by a screw driver or another tool to be fitted back into the seat 16, such that the locking element 39 may be moved back into the lifted position.
In this position, the rims 46 of the wings 45 are spaced from the annular projection 48 and promote the rotation of the lower portion 41 of the sheet element 38 to form an angle β+Δβ. In this state, the upper portion 40 of the sheet element 38 is rotated by Δβ such that it is lowered and allows the terminal E to be slid off.
In the embodiment of the invention as shown in FIGS, 14 to 16, the casing 2 may have a substantially box-like shape and the body 14 may have quick-connect means 57 for promoting removable fixation of the casing 2 to a connecting base joined with the panel P, and not shown.
Otherwise, the quick-connect means 57 may promote connection of the casing 2 to the bottom of a push button box, also not shown.
Conveniently, a cylinder or cone 58 of clear material may be held within the case 2, such that it projects at least partially out of the casing 2 and is placed above the light source 9 to filter the light radiation R emitted therefrom and convey it almost entirely outwards.
The device of the invention is susceptible to a number of changes and variants, within the inventive concept disclosed in the appended claims. All the details thereof may be replaced by other technically equivalent parts, and the materials may vary depending on different needs, without departure from the scope of the invention.
While the device has been described with particular reference to the accompanying figures, the numerals are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Industrial applicability

The present invention may find application in industry, because it can be manufactured on an industrial scale in factories for production of electric devices and may be used on circuits, systems and machines for industrial and commercial applications.

Claims

An indicator device (1) for connection to a pair of terminals (E) of an electric system (I) and fixation to a panel (P) of a machine electric box and/or of a pushbutton box, which device (1) comprises:
- a casing (2) designed to be secured to the panel (P) of a machine and/or to a pushbutton box and defining a longitudinal axis (L);

- an electronic board (3) housed in said casing (2) and having a top face (4) and a bottom face (5) ;

- a pair of conductive pads (8) arranged on the bottom face (5) of said board (3);

- at least one light source (9) mounted on the top face (4) of said board (3) and having a pair of contacts (10) electrically connected to said pair of pads (8);

- connecting means (13) for electrically connecting said pads (8) directly with the terminals (E) of the system (I);
wherein said casing (2) is made of a first insulating base material and said board (3) is made of a second insulating base material having a maximum compression strength (C_max) of predetermined value;
wherein said casing (2) comprises a body (14) designed to be secured to the panel (P) and a bottom member (15) having a pair of seats (16) for housing said connecting means (13) and wherein said connecting means (13) comprise pressure elements (17) ;
characterized in that an electronic circuit (7) is mounted on the top face (4) of said board (3), and said board (3) has a main extension plan (X) which extents perpendicularly to said longitudinal axis (L), said first base material of said casing (2) being selected to have a maximum tensile strength (T_max) lower than the maximum compression strength (C_max) of the second base material of the board (3), said pressure elements (17) being configured for exerting on said pads (8) a stress (S) smaller than said predetermined value of maximum compression strength (C_max) of the second base material of the board (3).
Device as claimed in claim 1, characterized in that said bottom member (15) comprises a substantially planar bottom wall (18) having a pair of passages (19) communicating with said seats (16) for allowing the access of said connecting means (13).
Device as claimed in claim 1, characterized in that said pressure elements (17) comprise a pair of screws (32) housed in said seats (16) and insertable into respective through holes (33) formed on said board (3) in correspondence of said pair of pads (8), said screws (32) being designed to be tightened into a correspondent pair of blind holes (34) formed in said body (14) in alignment with said through holes (33).
Device as claimed in claim 3, characterized in that said first base material of said casing (2) is selected in the group of plastic materials having a tensile strength (T_max) smaller than said compression strength (C_max) to limit stresses (S) generated on said board (3) by said screws (32) when these latter are tightened into said blind holes (34).
Device as claimed in claim 3, characterized in that said screws (32) comprise an enlarged head (37) facing said pads (8) and designed to come into contact with the terminals (E) of the system (I).
Device as claimed in claim 2, characterized in that said pressure members (17) comprise a pair of metal sheet elements (38) inserted into said seats (16) and a pair of locking elements (39) acting on said sheet elements (38) and housed in said seats (16).
Device as claimed in claim 6, characterized in that each of said sheet elements (38) is movable between an engagement position, and respectively a disengagement position, with one of the terminals (E) for electrically connecting this latter with said pads (8).
Device as claimed in claim 7, characterized in that each of said sheet elements (38) comprises an upper end portion (40) designed to come into contact with one respective terminal (E) and a lower end portion (41) designed to interact with one respective locking element (39).
Device as claimed in claim 8, characterized in that said bottom end (15) comprises a transverse wall (50) having a lower surface (51) delimiting said seats (16) and an upper surface (52) delimiting a connection area (53) for connecting the terminals (E) with said pads (8), said transverse wall (50) being provided with a first pair of slots (54) for the passage of the upper end portions (40) of said sheet elements (38) in said connection area (53).
Device as claimed in claim 1, characterized in that said body (14) of said casing (2) has a substantially tubular shape and insertable into a hole (A) of the panel (P), said body (14) being designed to be anchored in the hole (A) by an annular sleeve (20) internally threaded apt for tightening it to a thread (21) formed on the side surface (22) of said body (14).
Device as claimed in claim 1, characterize in that said casing (2) has a substantially box-like shape.