Electromagnetic safety relay

Abstract

 An electromagnetic safety relay (90) comprising a coil (10) wound about a core, a metal frame (20), a movable armature (30) secured to the frame (20) and used to operate an assembly of contact carrier strips (50) consisting of fixed strips (5F) and mobile strips (5M), an actuator (40) guiding the movement of the strips (50), and a return spring (80) positioned below the frame (20) such that the system of active forces (given by the movable armature (30)) and of reactive forces (given by the return spring (80)) is asymmetric, ie is applied on the same side of the actuator (40). This constructional arrangement enables the fixed contact carrier strips (5F) to be given sufficient rigidity and enables a single compact and robust actuator model (40) to be used for the various configurations of the electrical contacts (70) of the relay (90). Moreover, differential malfunctions between the two sides of the assembly of electrical contacts (70) are prevented and it becomes possible to determine and indicate anomalies in the case of breakage of the actuator (40) with the relay (90) energized.

Description

[0001] This invention relates to an electromagnetic safety relay, or an electrically controlled switch for the semi-automatic making or breaking of a circuit.

[0002] Traditional devices of this type comprise a magnetic circuit, an insulating body and a group of contact carrier strips operated by an actuator.

[0003] The magnetic circuit usually comprises a coil wound about a core, a metal frame and a movable armature, which is maintained suspended by a projection provided on the relay frame (the so-called magnetic circuit "jacketing") and is secured to the frame itself.

[0004] When the magnetic circuit is powered, the transfer of the force exerted by the coil on the movable armature drags the actuator and the contact carrier strips connected to it.

[0005] The insulating body acts as a support for the assembly and a container for the contact carrier strips. It supports the magnetic circuit (in an upper region of the insulating body) and contains the contact carrier strips (in a central region of the insulating body) and the actuator, which is inserted into the base between the strip terminals.

[0006] A return spring is shaped and arranged such that, being positioned in its seat below the frame at one end and hooked at its other end to the actuator, it is put under tension to maintain the actuator in the rest position. On electrically operating the relay the spring acquires the required return force by virtue of its deformation.

[0007] Electromagnetic relays of this type are very widespread in the electrotechnical industry, however they suffer from a series of drawbacks, the negative effects of which inevitably affect its technical performance in terms of time and/or its manufacturing cost, and which it would be advantageous to eliminate or at least reduce.

[0008] Firstly, if a contact were to become welded, the substantial elasticity of the contact carrier strips could result, in known relays, in movement of the actuator linked to the welded strip, so causing the other contacts to complete their own movement. Hence stops have to be provided on the fixed strips to prevent them being dragged in the case of a fault, and ensure that all contacts assume the intermediate position (safety position).

[0009] Moreover, the present configurations used for such electromagnetic relays include the insertion of a longitudinal insulating baffle, to improve separation between the contacts and hence requiring actuators split between the two sides of the dividing baffle of the contact cage (U-shaped configuration).

[0010] In most known relays, the system of applied active and reactive forces is symmetrical about the actuator, the reactive force being determined by the contact carrier strips themselves or by a spring positioned on the opposite side of the movable armature.

[0011] In this manner the actuator operates under compression.

[0012] These two design factors (the special actuator configuration and the force symmetry) make it possible for differential faults to arise between the right and left sides of the contact assembly, an actuator fault generally having unpredictable effects, depending on the manner in which the arms of the actuator U-piece break or wear.

[0013] Finally, a space is provided in the insulating body in proximity to the coil connections to house auxiliary electronic components, such as diode bridges, capacitors, etc.

[0014] An object of this invention is therefore to provide a fault-proof electromagnetic safety relay which obviates the aforesaid drawbacks, ie an electromagnetic safety relay which presents numerous advantages over the known art, both in terms of electrical performance and in terms of versatility and efficiency.

[0015] Further object of the invention is to construct an electromagnetic safety relay which satisfies the national and international electrotechnical standards.

[0016] A further object of the invention is to construct an electromagnetic safety relay at low cost, without using complex or costly techniques. These objects are attained by an electromagnetic safety relay in accordance with claim 1, to which reference should be made for brevity. Advantageously, the relay of the invention uses special constructional expedients for the contact carrier strips, the actuator and the return spring, to provide high electrical performance and substantial safety in use.

[0017] One of the special characteristics of the invention is the fact that the contact carrier strips are insertion-fixed at their ends and shaped such that they extend downwards relative to the coil.

[0018] This constructional arrangement arises from the need to give the fixed contact carrier strips sufficient rigidity without having to provide movement stops or special stiffening shapes for the strip.

[0019] In this manner it is also possible to use the strip as an outlet terminal.

[0020] In addition, the relay movement actuator is inserted into the base of the insulating body, so as to require only one actuator model for the various contact configurations. It consists of a single suitably shaped compact element provided with strip insertion guides, and can be likened to a beam supported at one end and suspended at the other by the return spring.

[0021] The actuation system is very robust by virtue of consisting of a single element. This means that differential faults between the right side and left side of the contact assembly are prevented.

[0022] Finally, the system of active (given by the movable armature) and reactive (given by the return spring) elastic forces is asymmetric, ie is applied to the same side of the actuator.

[0023] This means that actuator breakage causes certain opening of the last contact (usually used as the self-retaining), so preventing the relay being able to give the impression that it is still undamaged even when in fact it is broken, in contrast to what experience has shown with known relays.

[0024] Further objects and advantages of the invention will be apparent from the ensuing description and the accompanying drawings, which are provided by way of non-limiting example and on which:

Figure 1 is a schematic view of the electromagnetic safety relay of this invention;

Figure 2 is a side view of the contact carrier strips of the electromagnetic relay of the invention.

[0025] In said figures, the reference numeral 90 indicates overall an electromagnetic safety relay according to the invention, 10 indicates a coil wound about a core, 20 indicates a metal frame, 30 indicates a movable armature, and 40 indicates an actuator element which drags an assembly of contact carrier strips, indicated overall by 50, which are secured to it.

[0026] The actuator 40 is provided at one end with two outer cylindrical projections indicated by 9A, and at the other end with a coupling element indicated by 9B.

[0027] The contact carrier strips 50 are elastic and comprise strips of fixed type (indicated by 5F) and of mobile type (indicated by 5M).

[0028] They are of different and rather complicated shapes in order to satisfy the various functions for which they are intended, and are all inserted into a cage or insulating body 60 in such a manner as to be fixed at their ends.

[0029] The mobile contact carrier strips 5F are provided with a lance-like tip 5P to enable them to be inserted into the guides of the actuator 40.

[0030] The reference numeral 70 indicates the electrical contacts of the relay 90, these being positioned below the coil 10 and above the actuator 40, the reference numeral 80 indicating a return spring.

[0031] The fixed contact carrier strips 5F are of such a thickness that each can be used at one end as a terminal for its fixing onto a printed circuit.

[0032] The fixed strip 5F is structurally in the form of a beam fixed at both ends, its elasticity being determined exclusively by a short longitudinal cut, this elasticity being limited to ensure that each fixed strip 5F accompanies the mobile strip 5M.

[0033] This particular shaping means that no blocking element (such as stops, teeth, etc.) is required because should the electrical contacts 70 become welded together for any reason, the limited elasticity of the strip 5F prevents movement of the actuator 40, which is linked to the welded mobile strip 5M, and the consequent closure of the other electrical contacts 70.

[0034] Each mobile contact carrier strip 5M can be separated into two separate elements, namely a support which acts as an outlet pin and, as in the case of each fixed strip 5F, is fixed at both ends, and an actual lamina of smaller thickness than the fixed strips 5F and inserted upperly into the cage or insulating body 60. The lower end of this element is secured to the actuator 40, which moves it.

[0035] The contact carrier strips 50 are shaped to extend downwards from the coil 10, and are isolated in pairs within the insulating body 60. These very special characteristics, together with the use of an adequate thickness for the strips 50, arise from the requirement to give the fixed contact carrier strips 5F sufficient rigidity not to have to provide movement stops or special stiffening shapes for the strip 5F.

[0036] In this manner it is also possible to use the strip 50 directly as an outlet terminal.

[0037] The mobile contact carrier strips 5M are also provided with a tip 5P in the form of a lance, to enable it to be inserted into the guides of the actuator 40.

[0038] The actuator 40 is located in the base of the cage or insulating body 60, to enable it to move below the fixed contact carrier strips 5F. The suitably shaped mobile contact carrier strips 5M are instead secured to it.

[0039] This arrangement enables a single actuator model 40 to be provided for the various configurations of the electrical contacts 70 and hence for the different versions of the relay 90, in that as the actuator 40 moves within the base of the insulating body 60, it does not interfere with the fixed contact carrier strips 5F but only with the mobile ones 5M.

[0040] At an outer end, the actuator 40 is provided with two cylindrical projections 9A which enable it to slide within suitable seats of the insulating body 60. At its opposite end, the actuator 40 is coupled at 9B to a return spring 80.

[0041] Statically it can be considered as a beam suspended at one end from the return spring 80 and resting at its other end in two seats, so reducing the friction in play to a practically negligible level.

[0042] According to the invention, the actuator 40 consists of a single suitably shaped compact, robust element provided with insertion guides for the strips 50. This construction makes any breakage of the actuator 40 extremely improbable, as it does any malfunction due to differential faults present on only one of the sides of the insulating body 60 as in known relays 90 comprising actuators 40 of U-configuration, ie split between the two sides of the insulating body 60.

[0043] The return spring 80 is shaped and bent such that when positioned in its seat below the frame 20 and coupled to the end 9B of the actuator 40, it is placed under pretension to maintain the actuator 40 in its rest position. On electrically operating the relay 90, the return spring 80 acquires the force required to return directly from its deformation.

[0044] In most known electromagnetic relays the active and reactive force system in play is symmetrical about the actuator 40. The reactive force is determined by the strips themselves, or by a spring positioned on the opposite side of the actuator 40.

[0045] However, in this manner any breakage of the actuator 40 can have unpredictable consequences, as the relay could continue to operate degraded, even with the actuator broken.

[0046] In contrast, with this invention the active and reactive force system is asymmetric, ie is applied on one and the same side of the actuator 40. In the case of breakage of the actuator 40 with the relay energized, this arrangement enables the mobile contact carrier strips 5M situated downstream of the breakage point to assume a neutral position, to provide a certain fault indication.

[0047] In this respect, by using the normally open contacts positioned on the opposite side of the movable armature as self-retaining, actuator breakage is immediately and safely indicated by de-energization of the relay.

[0048] In this case the elastic force system comprises an active force provided by the movable armature 30, and a reactive force provided by the return spring 80.

[0049] The characteristics of the electromagnetic safety relay are apparent from the aforegoing description, as are the resultant advantages.

[0050] These particularly include:

• better electrical performance than the known art;
• greater protection against unpredictable relay malfunction than the known art;
• greater relay compactness and robustness than traditional devices;
• standardized constructions;
• better ergonomics and more efficient fault or malfunction diagnosis than the known art;
• national and international electrotechnical standards satisfied;
• lower costs and more simple and less costly manufacture than the known art.

[0051] Finally, numerous modifications can be made to the electromagnetic safety relay of this invention without leaving the principles of novelty inherent in the inventive idea, it also being apparent that in the practical implementation of the invention, the materials, shapes and dimensions of the illustrated parts can be chosen at will according to requirements, and that these can be replaced by others technically equivalent.

Claims

1. An electromagnetic safety relay (90), of the type comprising a magnetic circuit, an insulating body (60) and a plurality of contact carrier strips (50) operated by an actuator (40) and with which there are associated a plurality of electrical contacts (70), said magnetic circuit consisting of a coil (10) wound about a core, a metal frame (20), and a movable armature (30) secured to said frame (20) and used to operate the contact carrier strips (50), said actuator (40) transmitting to the contact carrier strips (50) secured to it the movement generated by said movable armature (30) and being maintained in a rest position by a return spring (80) put under pretension, said return spring (80), situated below said frame (20), acquiring the force necessary to return from its own deformation following electrical operation of the relay (90), characterised in that said contact carrier strips (50) are fixed at their ends and are arranged such that they extend downwards relative to the natural position of the relay (90), said electrical contacts (70) being provided on the lower part of said strips (50).

2. An electromagnetic relay (90) as claimed in claim 1, characterised in that said actuator (40) is positioned within the base of the insulating body (60) below said electrical contacts (70), between the terminal elements of the contact carrier strips (50).

3. An electromagnetic relay (90) as claimed in claim 1, characterised in that said contact carrier strips (50) are elastic and are isolated in pairs within said insulating body (60).

4. An electromagnetic relay (90) as claimed in claim 3, characterised in that said contact carrier strips (50) comprise at least one fixed strip (5F) and at least one mobile strip (5M) which are of mutually different shape, said fixed strip (5F) being fixed at its ends, said mobile strip (5M) being separable into two distinct elements.

5. An electromagnetic relay (90) as claimed in claim 4, characterised in that each mobile contact carrier strip (5M) can be separated into a first support element fixed at its ends, and a second element which is of lesser thickness than the first and is attached at one end to the first support element, while at its other end it is secured to said actuator (40), which moves it.

6. An electromagnetic relay (90) as claimed in claim 4, characterised in that said fixed strip (5F) consists structurally of a beam fixed at its ends, its elasticity being determined by at least one cut provided along a longitudinal portion, to ensure that it accompanies said mobile strip (5M).

7. An electromagnetic relay (90) as claimed in claim 4, characterised in that said fixed strip (5F) has a thickness enabling it to be used at one end as a terminal for its fixing onto a printed circuit.

8. An electromagnetic relay (90) as claimed in claim 4, characterised in that each mobile contact carrier strip (5M) is provided with at least one tip (5P) in the form of a lance, to enable it to be inserted into the actuator (40).

9. An electromagnetic relay (90) as claimed in claim 2, characterised in that said actuator (40) consists of a single model for the various configurations of the electrical contacts (70).

10. An electromagnetic relay (90) as claimed in claim 2, characterised in that said actuator consists of a single suitably shaped robust, compact element provided with a plurality of guides for the insertion of said contact carrier strips (50).

11. An electromagnetic relay (90) as claimed in claim 10, characterised in that said actuator (40) is provided at a first end with at least one cylindrical projecting element (9A) enabling it to slide within an appropriate seat in the insulating body (60), and is provided at a second end with at least one element (9B) for its coupling to said return spring (80).

12. An electromagnetic relay (90) as claimed in claim 1, characterised in that the system of active elastic forces relative to said movable armature (30) and of reactive elastic forces relative to said return spring (80) is assymetric, ie is applied on one and the same side of said actuator (40).

Drawing