Contact unit

Claim 2

An add-on contact unit for an electromagnetic switching device operable between a deenergized, spring biased first postion and an energized second position, said add-on contact unit comprising, in combination: actuating means positively coupled to the actuator of said switching device; a plurality of contact sets operated by said actuating means, at least one contact set being normally closed when said switching device is in said first position; contact pressure springs for each contact set operating between said contact set and said actuating means, said contact pressure spring of said normally closed contact set and said spring biasing said switching device to said first position providing parallel, oppositely disposed spring forces; and means retaining said actuator means and said switching device in said first position against the bias of said contact pressure spring for said normally closed contact set and against the operating force of said switching device upon energization until the latter force exceeds a threshold value.

Claim 3

An electrical contact unit as claimed in claim 1, in which the actuating means comprises a linearly-movable member and in which the retaining means comprises a transverse channel in said linearly-movable member, a ball bearing urged outwardly from said channel and a body member including a shoulder behind which the ball bearing engages when the contact set is closed.

Claim 4

An electrical contact unit as claimed in claim 2, in which the retaining means includes a helical spring located in said channel to urge said ball bearing outwardly thereof.

Claim 5

An electrical contact unit as claimed in claim 1, in which the actuating means comprises a linearly movable member and in which the retaining means comprises a transverse channel formed through said linearly-movable member, a pair of ball bearings located at opposite ends of said channel, a helical spring located in said channel between said ball bearings to urge the ball bearings outwardly from opposite ends of said channel and a body member against which the ball bearings are urged and including a shoulder behind which one of the ball bearings engages when the contact set is closed.

Claim 6

An add-on contact unit for an electromagnetic switching device, said switching device having an electromagnet energizable to attract an armature thereto against the bias of an armature return spring, a plurality of contact sets operable to circuit making or circuit breaking conditions and an actuating member affixed to said armature for operating said contact sets; said contact unit comprising, in combination: actuating means coupled to said actuating member for positive movement therewith, said actuating means being biased to a first position by said armature return spring and being operable to a second position by energization of said electromagnet; a plurality of contact sets operated by said actuating means and having contact pressure springs disposed between the movable contacts thereof and said actuating means; at least one of said contact sets being normally closed when said actuating means is in said first position, said contact pressure spring of said normally closed contact set providing a force on said actuating means which is parallel and oppositely directed to the operating force provided by said armature return spring; and means for retaining said actuating means in said first position against the opposing force of said contact pressure spring and against the subsequent operating force of said electromagnetuntil the latter exceeds a threshold value.

Claim 7

An add-on contact unit for an electromagnetic switching device, said switching device having an electromagnet energizable to attract an armature thereto against the bias of an armature return spring, a plurality of contact sets operable to circuit making or circuit breaking conditions and an actuating member affixed to said armature for operating said contact sets; said contact unit comprising, in combination: actuating means coupled to said actuating member for positive movement therewith, said actuating means being biased to a first position by said armature return spring and being operable to a second position by energization of said electromagnet; a plurality of contact sets operated by said actuating means and having contact pressure springs disposed between the movable contacts thereof and said actuating means; at least one of said contact sets being normally closed when said actuating means is in said first position, said contact pressure spring of said normally closed contact set providing a force on said actuating means which is parallel and oppositely directed to the operating force provided by said armature return spring; and means for retaining said actuating means in said first position against the opposing force of said contact pressure spring and against the subsequent operating force of said electromagnetuntil the latter exceeds a threshold value.

Claim 8

An add-on contact unit for an electromagnetic switching device, said switching device having an electromagnet energizable to attract an armature thereto against the bias of an armature return spring, a plurality of contact sets operable to circuit making or circuit breaking conditions, and an actuating member affixed to said armature for operating said contact sets; said contact unit comprising, in combination: a housing attached to said switching device; actuating means linearly movable in said housing and coupled to said actuating member for positive movement therewith; a plurality of contact sets each having stationary contacts mounted in said housing and a respective movable contact carried by said actuator means, at least one of said contact sets being normally closed wherein the respective movable contact is in circuit making engagement with the cooperating stationary contacts thereof when said electromagnet is deenergized, said armature, actuating member and actuating means being extended under the bias of said return springs; contact pressure springs for said contact sets, said springs being operable between said actuator means and said movable contacts to bias said movable contacts into engagement with said stationary contacts, said spring for said normally closed contact set providing a parallel and oppositely disposed force to that of said return spring; and means retaining said actuator means in the extended position thereof against the bias of said contact pressure spring of said normally closed contact and against an actuating force applied by said electromagnet until the latter force exceeds a threshold value.

Claim 9

An add-on contact unit for an electromagnetic switching device, said switching device having an electromagnet energizable to attract an armature thereto against the bias of an armature return spring, a plurality of contact sets operable to circuit making or circuit breaking conditions, and an actuating member affixed to said armature for operating said contact sets; said contact unit comprising, in combination: a housing attached to said switching device; actuating means linearly movable in said housing and coupled to said actuating member for positive movement therewith; a plurality of contact sets each having stationary contacts mounted in said housing and a respective movable contact carried by said actuator means, at least one of said contact sets being normally closed wherein the respective movable contact is in circuit making engagement with the cooperating stationary contacts thereof when said electromagnet is deenergized, said armature, actuating member and actuating means being extended under the bias of said return springs; contact pressure springs for said contact sets, said springs being operable between said actuator means and said movable contacts to bias said movable contacts into engagement with said stationary contacts, said spring for said normally closed contact set providing a parallel and oppositely disposed force to that of said return spring; and means retaining said actuator means in the extended position thereof against the bias of said contact pressure spring of said normally closed contact and against an actuating force applied by said electromagnet until the latter force exceeds a threshold value.