Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Multiple contact type
Reexamination Certificate
2001-01-24
2003-12-09
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Multiple contact type
C335S130000, C335S083000
Reexamination Certificate
active
06661320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a relay and more particularly a safety relay with an electrically insulating carrier part and an electromagnetic drive arranged on the carrier part, at least one control contact and at least three load contacts, both the load and control contacts being forcibly guided. In such a relay, the contacts are individually comprised of two essentially parallel, flat contact springs, each spring comprising a contact head, a spring foot at a distance to the contact head and at least one fastener part connected to the spring foot, for example one or two pins. The spring feet of the contact springs are rigidly fixed on the carrier part. The invention also concerns a three-phase supply network capable of being switched by such a safety relay and the circuitry associated with such a safety relay.
2. Brief Description of Art
As used herein, the term “forcibly guided” refers to the property of being linked by a common movable comb. Therefore, a forcibly guided relay is one in which the contacts are mechanically linked by a common movable comb, connected with the drive and in which at least one working contact and one resting contact are provided. In such a relay, one of the contact springs of each contact is next to a fixed stop in the vicinity of the head, and the other contact spring is engaged in such a way in the comb that it is mechanically linked to the movements of the comb. In this way, it is assured that if a contact is welded, either this contact is broken, or the comb cannot be moved and thus the other contacts must remain in the position produced by the welded contact.
The term “safety relay” means a relay in accordance with standard EN (European Standard) 50205. In a safety relay according to standard EN 50205, the air paths and leakage paths between the control contact and the load contact correspond to the requirements of standard IEC 61810-5 and IEC 664-1. The contents of these standards incorporated in their entirety herein by reference.
For switching electric devices consuming electrical current wherein a high safety standard must be met, two safety relays and two downstream-connected contactors are used. Examples of such current consumers include three-phase current motors. Such circuitry is appropriate for devices having loads, for example, of more than 6 kW. However, devices with loads of approximately 1 to 4 kW are also connected in the described manner and the contactor used therein would be suitable for significantly greater loads. Three-phased motors with a load current, for example, of 5.6 A (constant current) and a switching-on peak-current of approximately 40 A cannot be switched with known safety relays without the provision of an overdimensioned contactor. This requires a nonnegligible expenditure for wiring. In such wiring, each relay and contactor is a relatively expensive part in the production of the circuitry and represents separate possible sources of error.
BRIEF SUMMARY OF THE INVENTION
It is the object of the present invention to increase the safety of switching current, such current switching relative to three-phase mains current, while reducing the structural volume of the required parts. For this purpose, in particular, the number of parts for switching and the possible sources of error in the circuit of current consumers, especially of short-circuit-resistant, three-phase electric motors of 1 to 4 kW power, will be reduced. In addition, a forcibly guided relay will be created, which is designed for voltages of more than 110V or 250V, particularly the 200 or 400V relative voltage between phases that occurs in three-phase mains current, that fulfills the requirements of a safety relay with forcibly guided contacts.
A reduction in the number of parts and a reduction in the number of error sources will be resolved according to the invention by using a forcibly guided safety relay for switching the three phase circuit of a three-phased mains voltage connected to the three load contacts. Appropriately, two relays connected in series are used for the synchronous switching of the three phases in the two relays. By the use of the relay for the direct switching of the consumer current, two contactors connected downstream to the relay and the corresponding wiring of the contactors can be dispensed with. The reduction in the number of parts is accompanied by a reduction in possible sources of error. The double design of the relay serves for safety. It is immaterial whether the two relays are connected in series or if one double relay is utilized.
In a circuit for a three-phase main-current consumer, particularly a short-circuit-resistant electric motor with a forcibly guided safety relay, the three phases of the mains current are connected to the load contacts of the safety relay according to the invention. Here also, for purposes of safety, two safety relays connected in series as two separate relays or together in the form of a double relay are appropriately provided.
Accordingly, one aspect of the invention is drawn to a safety relay comprising an electrically insulating carrier part, an electromagnetic drive arranged on the carrier part, at least one control contact arranged on the carrier part, at least three load contacts arranged on the carrier part. Each of the load and control contacts is forcibly guided by a common comb connected with the electromagnetic drive and has two contact springs, each of the contact springs comprising, a contact head, a spring foot at a distance from the contact head, and at least one fastener part connected with the spring foot. The contact springs are supported solidly with the spring foot in the carrier part. At least one of the contacts forms a working contact and another one a resting contact. A rigid stop is arranged on the carrier part next to which is located the contact head the rigid stop being in the vicinity of one of the contact springs, the other one of the contact springs of the contact engaging the comb in such a way that the movement of the contact spring is mechanically linked with the movements of the comb. At least one insulating dividing wall for separating the contact springs of the load contacts is reaching from the spring foot at least to the vicinity of the contact head and extending from one side to the other of the safety relay. The dividing wall has an offset on the sides bent in opposite directions. A continuous separating wall embracing the adjacent contact springs of the load contacts is formed by the bent offsets connecting the dividing wall with one of the adjacent dividing walls such that the dividing walls and the offsets form a continuous separating wall.
A second aspect of the invention is drawn to a three-phase supply network that comprises at least one safety relay to switch the three phases of the supply network. The relay comprising an electrically insulating carrier part, an electromagnetic drive arranged on the carrier part, at least one control contact arranged on the carrier part, at least three load contacts arranged on the carrier part. Each of said three load contacts is connected to one of said three phases and each of the load and control contacts is forcibly guided by a common comb connected with the electromagnetic drive. Each load and control contact has two contact springs, each of the contacts springs comprising, a contact head, a spring foot at a distance from the contact head, and at least one fastener part connected with the spring foot. The contact springs are supported solidly with the spring foot in the carrier part. At least one of the contacts forms a working contact and another one a resting contact. A rigid stop is arranged on the carrier part next to which is located the contact head. The rigid stop being in the vicinity of one of the contact springs, the other one of the contact springs of the contact engaging the comb in such a way that the movement of the contact spring is mechanically linked with the movements of the comb.
A third aspect of the invention is drawn to an electrical c
Donovan Lincoln
Elesta Relays GmbH
Kinney Michael K.
Simons William A.
Wiggin & Dana LLP
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