GB2341729A - Electrical relay incorporating ptc element - Google Patents

Electrical relay incorporating ptc element Download PDF

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Publication number
GB2341729A
GB2341729A GB9921772A GB9921772A GB2341729A GB 2341729 A GB2341729 A GB 2341729A GB 9921772 A GB9921772 A GB 9921772A GB 9921772 A GB9921772 A GB 9921772A GB 2341729 A GB2341729 A GB 2341729A
Authority
GB
United Kingdom
Prior art keywords
relay
load
coil
temperature coefficient
positive temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9921772A
Other versions
GB9921772D0 (en
Inventor
Christopher John Shakespeare
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MG Rover Group Ltd
Original Assignee
MG Rover Group Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MG Rover Group Ltd filed Critical MG Rover Group Ltd
Publication of GB9921772D0 publication Critical patent/GB9921772D0/en
Publication of GB2341729A publication Critical patent/GB2341729A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H50/00—Details of electromagnetic relays
    • H01H50/02—Bases; Casings; Covers
    • H01H50/021—Bases; Casings; Covers structurally combining a relay and an electronic component, e.g. varistor, RC circuit
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • H02H9/026—Current limitation using PTC resistors, i.e. resistors with a large positive temperature coefficient

Abstract

An electrical relay <B>10</B> comprises a coil <B>16</B> wound around an iron core <B>14</B> which in use produces a magnetic field when a electric current is passed therethrough. The magnetic field may influence the movement of an armature <B>20</B> which may pivot about a fulcrum <B>22</B> at the upper end of a yoke <B>24</B>. The armature is biased by a spring <B>26</B> into a position in which the contacts are normally open. Upon magnetisation of the coil, the armature <B>20</B> closes the contacts <B>18</B> and provides a load line through the relay <B>10</B>. A positive temperature coefficient element (PTC) <B>28</B> which may be of polymer material is integrated with a connection member <B>LP1</B> of the relay <B>10</B>, said connection members allowing connections to made between the coil <B>16</B> and switching portions <B>18</B> and external circuits. The relay may take the form of a change over relay (see fig. 2) in which the armature can open / close contacts with two different load lines. The positioning of the PTC element can determine which load lines are provided with over-current protection.

Description

2341729 An Electrical Relav This invention relates to electrical relays an
in particular to a relay which includes means for thermal protection.
It is a disadvantage of some known electrical relays that it is advisable to protect the relay and/or the load driven by such a relay by including an in-line fuse. The provision of an additional circuit element incurs increased manufacturing costs and may be subject to packaging constraints.
It is an object of this invention to provide an improved electrical relay.
According to the invention there is provided an electrical relay comprising a coil portion which is arranged in use to produce a magnetic field when an electrical current is passed therethrough and a switching portion which is arranged in use, in response to said magnetic field, to control the passage of a load current through a load line of the relay, the relay also comprising a plurality of external connection members which are arranged to allow a connection to be made from each of the coil portion and the switching portion to an external circuit, the relay further comprising a lead frame which is integral to the relay and which is arranged to provide a said connection between a said external connection member and an associated one end of the coil portion or the switching portion, wherein a positive temperature coefficient element is included in said connection between said external connection member and the associated coil end or switching portion.
The positive temperature coefficient element may be included by at least one of, or a combination of, a pressure connection and a solder '5 connection.
The relay may comprise a further positive temperature coefficient element, which is integrated with another external connection member or with an internal connection member.
The positive temperature coefficient element may comprise a polymer 10 material and may comprise a wafer construction.
The relay may comprise an International Standards Organisation (ISO) relay footprint, whereby the relay may be arranged to be backward compatible so that it can be retro-fitted to a circuit as a replacement for an originally fitted relay and/or to provide a thermal fuse for a circuit which 15 may not have originally been provided with over-current protection. - The relay may comprise a normally open relay. In the alternative, the relay may comprise a change-over relay. and a positive temperature coefficient element may be included in series with a said connection on the 3- common side of a set of load contacts which comprise a change-over portion of the relay.
A positive temperature coefficient element may be included in series with a said connection which is in series with a load contact on the non5 common side of the relay.
The invention will now be described by way of example with reference to the accompanying drawings, in which:
Figure 1 is a section through an electrical relay according to a first embodiment of the invention: and Figure 2 is a section through a relay according to a second embodiment of the invention.
Referring to Figure 1. in a first embodiment of the invention an t electrical relay 10 comprises a housing 12 in which are contained a coil portion and a switching portion.
The coil portion comprises a soft iron core 14 around which is wound a coil 16. Each end of the coil 16 is connected to an internal connection member in the form of a coil pin CP which allows the coil 16 to be connected to an electrical circuit (not shown) which is external to the relay 10.
The relay 10 includes an integral lead frame LF1, through which the coil pins CP, and therefore the coil 16, are interfaced to external connection members CPext via respective lead frame connections LF1cl).
The switching portion comprises pair of contacts 18, one of which is 'D mounted on an internal connection member in the form of a first load pin LP1 and the other of which is mounted on a movable armature 20. The armature 20 is movable by a pivoting action about a fulcrum 22 in the region of the upper end of a voke 24. The armature 20 is biased by a spring 26 into a position in which the contacts 18 are normally open, the spring 26 also providing an electrical connection between the end portion of the armature 20 opposite to the contacts 18 and a second load pin LP2 which forms, in combination with the first load pin LP1, a load line through the relay 10.
In similar fashion to the coil pins CP, the load pins LP1, LP2 are connected to external connection members LP1ext, LP2ext through the lead frame LF1 by respective connections LP10, LP20.
When an electrical current, the coil current, is passed through the coil 16, the core 14 becomes magnetised and pulls the armature 20 down in a solenoid type of action, thereby closing the contacts 18 and providing a load line between the load pins LP1, LP2 and allowing a load current to flow through the relay 10.
When the coil current is switched off, the core 14 becomes demagnetised and the biasing of the spring 26 pivots the armature 20 about the yoke 24, which in turn causes the contacts 18 to open and cut off the passage of any load current.
A positive temperature coefficient element (PTC) 28 is included in the lead frame LF1 and is integrated into the connection LP10 between the first load pin LPI and its external connection LP1ext and the PTC 28 is thus put in series with the path of any load current. In a variation to the invention, the PTC 28 could be integrated into the lead frame connection LP20 between the other load pin LP2 and its external connection LP2ext, whilst still protecting the relay 10 from any excessive load current.
The PTC 28 comprises a polymer mate-ial, is of wafer construction and is integrated into the connection LP10 by soldering. The PTC 28 could also be integrated by pressure (e.g. a crimped connection) or by a combination of pressure and soldering.
The PTC 28 has a characteristic curve which is chosen to be appropriate for the load currents that the relay 10 is likely to have to pass. At a specified level of over-current, the resistance of the PTC 28 will rise to a level (e.g. to several kQ or more) where it acts as a thermalfuse and cuts off the load current. On cooling over time, the resistance of the PTC 28 will drop to a level (e.g. a few hundred mQ) at which the load current may once 5 again flow along the load line.
Referring now to Figure 2, in a second embodiment of the invention an electrical change-over relay 100 comprises a housing 120 in which are contained a coil portion and a switching portion.
a The coil portion comprises a soft iron core 140 around which is wound a coil 160. Each end of the coil 160 is connected to an internal connection member in the form of a coil pin CPa, CPb which allows the coil 160 to be connected to an electrical circuit (not shown) which is external to the relay 100.
The relay includes an integral lead frame LF2, through which the coil pins CPa, CPb, and therefore the coil 160, are interfaced to external connection members CPaext, CPbext via respective lead frame connections LF2cp.
The switching portion comprises a set of change-over contacts 180, which are sub-divided into a switching contact 180a, a first load contact 180b and a second load contact 180c. The first load contact 180b is connected to an internal connection member in the form of a first load pin LP30b and the second load contact 180c is connected to an internal connection member in the form of a second load pin LP30c.
The switching contact 180a is mounted on a movable armature 200, which is movable by a pivoting action about a fulcrum 220 in the region of the upper end of a yoke 240. The armature 200 is biased by a spring 260 into a position in which the switching contact 180a is normally in contact with the first load contact 180b, the spring 260 also providing an electrical connection between the end portion of the armature 200 opposite to the contacts 180 and an internal connection member in the form of a third load pin LP30 which forms, in combination with which ever of the other load pins LP30b, LP30c is in contact with the switching contact 180a, a load line through the relay 100.
When an electrical current, the coil current, is passed through the coil 160, the core 140 becomes magnetised and pulls the armature 200 down in a solenoid type of action, thereby changing over the load line at the contacts 180 by moving the switching contact 180a out of contact with the first load contact 180b and into contact with the second load contact 180c and thus providing a load line between the load third load pin LP30 and the second load pin LP30c.
When the coil current is switched off, the core 140 becomes demagnetised and the biasing of the spring 260 pivots the armature 200 about the fulcrum 220, which in turn causes the switching contact 180a to move out of contact with the second load pin LP30c and back into contact 5 with the first load pin LP30b.
In similar fashion to the coil pins CPa, CPb, the load pins LP30b, LP30c are connected to respective external connection members LP30bext, LP30cext and the third load pin LP30 to its own external connection member LP30ext. These respective connections LP300b, LP300c, LP300 are made in the lead frame LF2.
A positive temperature coefficient element (PTC) 280 is included in the lead frame LF2 and is integrated into the connection LP300 between the third load pin LP30 and its external connection LP30ext.
The PTC 280 comprises a polymer material, is of wafer construction 15and is integrated into the connection LP300 by soldering. The PTC 280 could also be integrated by pressure (e.g. a crimped connection) or by a combination of pressure and soldering.
The PTC 280 has a characteristic curve which is chosen to be appropriate for the load currents that the relay 100 is likely to have to pass.
At a specified level of over-current, the resistance of the PTC 280 will rise to a level (e.g. to several kQ or more) where it acts as a thermal fuse and cuts off the load current. On cooling over time, the resistance of the PTC 280 will drop to a level (e.g. a few hundred m!Q) at which the load current may 5 once again flow along the load line.
In this example of the invention, the advantage of integrating the PTC 280 into the connection LP300 is that in that way both of the other load pins LP30b, LP30c are provided with over-current protection by a single PTC 280.
In a variation to the second embodiment, a PTC (not shown) could, in addition or in the alternative, be included in either or both of the first and second load pins LP30b, LP30c. In this manner, the relay 100 could be provided with independent over-current protection for each load served by the change-over between the first and second load pins LP30b, LP30c. An advantage offered by this variation of the second embodiment is that PTCs with different characteristics could be fitted to the load pins LP30b, LP30c when they LP30b, LP30c were used to provide a load line to loads drawing different currents.
In a possible modification to the embodiments described above, a further PTC (not shown) may, in the alternative or in addition, be 10- integrated into one or both of the coil pin lead frame connections LF1cp, LF2cp- In this manner it is possible to integrate one or more PTCs in series with either or both of the coil current and the load current on either side of the coil portion or the switching portion as appropriate and protect the 5 circuit.
In each embodiment, it is desirable for a relay 10, 100 which includes an integrated PTC element 28, 280 to retain a standard footprint, for example the International Standards Organisation (ISO) footprint. This allows a relay according to the invention to be backward compatible such that it could therefore be retro-fitted to a circuit which was originally produced using a relay with no thermal protection or so as to introduce thermal fusing.
CLMMS 1. An electrical relay comprising a coil portion which is arranged in use to produce a magnetic field when an electrical current is passed therethrough and a switching portion which is arranged in use, in response to said magnetic field, to control the passage of a load current through a load line of the relay, the relay also comprising a plurality of external connection members which are arranged to allow a connection to be made from each of the coil portion and the switching portion to an external circuit, the relay further comprising a lead frame which is integral to the relay and which is arranged to provide a said connection between a said external connection member and an associated one end of the coil portion or the switching portion, wherein a positive temperature coefficient element is included in said connection between said external connection member and the associated coil end or switching portion.

Claims (1)

  1. 2. A relay according to Claim 1, wherein the positive temperature
    coefficient element is included by at least one of, or a combination of, a pressure connection and a solder connection.
    3. A relay according to Claim 1 or Claim 2, comprising a further positive temperature coefficient element, which is integrated with another external connection member or with an internal connection member.
    4. A relay according to any preceding claim, the positive temperature coefficient element comprising a polymer material.
    5. A relay according to any preceding claim, the positive temperature coefficient element comprising a wafer construction.
    6. A relay according to any preceding claim, wherein the relay comprises an International Standards Organisation (ISO) relay footprint, whereby the relay may be arranged to be backward compatible so that it can be retro-fitted to a circuit as a replacement for an originally fitted relay and/or to provide a thermal fuse for a circuit which may not have originally been provided with over-current protection.
    7. A relay according to any preceding claim, comprising a normally open relay.
    8. A relay according to any one of Claims 1 to 6, comprising a changeover relay.
    13- 9. A relay according to Claim 8, wherein a positive temperature coefficient element is included in series with a said connection on the common side of a set of load contacts which comprise a change-over portion of the relay.
    10. A relay according to Claim 8 or Claim 9, wherein a positive temperature coefficient element is included in series with a said connection which is in series with a load contact on the non-common side of the relay.
    11. An electrical relay substantially as described herein with reference to Figure 1 or with reference to Figure 2 of the accompanying drawings.
GB9921772A 1998-09-17 1999-09-16 Electrical relay incorporating ptc element Withdrawn GB2341729A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB9820136.1A GB9820136D0 (en) 1998-09-17 1998-09-17 An electrical relay

Publications (2)

Publication Number Publication Date
GB9921772D0 GB9921772D0 (en) 1999-11-17
GB2341729A true GB2341729A (en) 2000-03-22

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GBGB9820136.1A Ceased GB9820136D0 (en) 1998-09-17 1998-09-17 An electrical relay
GB9921772A Withdrawn GB2341729A (en) 1998-09-17 1999-09-16 Electrical relay incorporating ptc element

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Application Number Title Priority Date Filing Date
GBGB9820136.1A Ceased GB9820136D0 (en) 1998-09-17 1998-09-17 An electrical relay

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1067571A2 (en) * 1999-07-05 2001-01-10 Volkswagen Aktiengesellschaft Relay module
WO2005076301A1 (en) 2004-02-06 2005-08-18 Tyco Electronics Raychem K.K. Switch and device using the switch
CN108346550A (en) * 2018-04-09 2018-07-31 合肥和旭继电科技有限公司 A kind of high power relay using Pneumatic Transmission
CN108493058A (en) * 2018-04-09 2018-09-04 合肥和旭继电科技有限公司 A kind of shock proof integrated motor relay

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2019925A1 (en) * 1989-06-30 1990-12-31 Paul R. Staples Ptc electromechanical relay

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2019925A1 (en) * 1989-06-30 1990-12-31 Paul R. Staples Ptc electromechanical relay

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1067571A2 (en) * 1999-07-05 2001-01-10 Volkswagen Aktiengesellschaft Relay module
EP1067571B1 (en) * 1999-07-05 2004-04-14 Volkswagen Aktiengesellschaft Relay module
WO2005076301A1 (en) 2004-02-06 2005-08-18 Tyco Electronics Raychem K.K. Switch and device using the switch
EP1720183A1 (en) * 2004-02-06 2006-11-08 Tyco Electronics Raychem K.K. Switch and device using the switch
EP1720183A4 (en) * 2004-02-06 2007-06-20 Tyco Electronics Raychem Kk Switch and device using the switch
CN1918679B (en) * 2004-02-06 2011-10-05 泰科电子雷伊化学株式会社 Switch and device using the switch
US8395062B2 (en) 2004-02-06 2013-03-12 Tyco Electronics Raychem Kk Switch and device using the switch
CN108346550A (en) * 2018-04-09 2018-07-31 合肥和旭继电科技有限公司 A kind of high power relay using Pneumatic Transmission
CN108493058A (en) * 2018-04-09 2018-09-04 合肥和旭继电科技有限公司 A kind of shock proof integrated motor relay

Also Published As

Publication number Publication date
GB9921772D0 (en) 1999-11-17
GB9820136D0 (en) 1998-11-11

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