Electricity: circuit makers and breakers – Electric switch details – Contact
Reexamination Certificate
1999-12-31
2001-08-07
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Contact
C200S255000, C200S554000
Reexamination Certificate
active
06271489
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to pressure switch contacts, and more specifically, to pressure switch devices having a cam locking mechanism to apply pressure at the contact points.
BACKGROUND OF THE INVENTION
There are numerous conventional pressure switches which utilize bolts and latches for applying pressure, or spring pressure configurations. Such conventional switches require adjustments in order to provide the desired amount of pressure at the contacts. Another disadvantage of conventional switches is the failure to provide a low pressure state before the switch is opened, or before the switch is closed, such that the pressure at the contact causes wear and stiffness during operation.
Conventional pressure switches often form unreliable electrical connections at the contacts when spring contacts are used. Furthermore, problems with contact sticking occur at elevated temperatures. Current induced thermal expansion of copper blades and terminals increases contact pressure in high rate spring pressure designs and may prevent the switch from opening if not carefully adjusted.
A further drawback of conventional switches is poor resistance to contact welding on fault closings.
Therefore, a reliable pressure switch which overcomes the above problems would be of great advantage in the electrical pressure switch industry.
SUMMARY OF THE INVENTION
In view of the above listed problems of the prior art, it is an object of the present invention to provide a pressure switch which does not require adjustment in order to provide the desired pressure.
It is another object of the present invention to provide a pressure switch device which provides a low-pressure state to facilitate opening and closing without excessive wear, yet maintains a reliable electrical connection.
It is a further object of the present invention to provide a pressure switch device which is easily opened and closed under high temperature conditions, and is more resistant to contact welding on fault closings.
In view of the above, and other advantages, a novel pressure switch is provided with a cam locking assembly. The switch has a jaw terminal and a hinge terminal. A blade assembly is pivotally mounted to the hinge terminal, and may rotate to engage the jaw terminal at a receiving portion.
The blade assembly preferably comprises two blades which straddle the terminal. The two blades are fastened to one another at either end via a fastener. The fastener preferably comprises a threaded bolt and a nut. A spacer is placed between the blades on each fastener to hold them in spaced relation, preferably slightly closer together than the distance across the terminals when in the open position.
A pair of cams is mounted at either end of the blade assembly. One cam of each pair may be fixedly mounted to the blade assembly. The cams may be mounted via the same fasteners holding the blades together. The other two of the pairs of cams are rotatably mounted. They are fastened to a rigid connecting link. Thus, movement of the connecting link will rotate the cams.
The cams are provided with protrusions, or raised portions, between one another such that when they are rotated into a locked position, they are forced apart, and increased pressure is applied forcing the blades closer together to engage the terminals. A spring washer is preferably mounted on each fastener to enhance the pressure. The spring washer flattens as the cams are rotated into the locked position.
A drive link is pivotally mounted to the blade assembly, and pivotally mounted to the connecting link. The drive link is preferably an insulating drive link. A drive shaft is mounted to the free end of the drive link via a crank pin. The drive shaft has a free end which is in fixed relation to the terminals, such as by affixing it to further mechanisms which enable its stability and rotation about a point near the free end.
As the drive link is rotated, the blade assembly moves from an open position to a closed position. Thus, the blade assembly is able to contact the receiving portion of the jaw terminal prior to the cams engaging. Further rotation of the drive shaft rotates the cams into engagement such that they are in a locked position and form a pressure engagement of the blades onto the terminals. In the locked position, the drive shaft forms a 180° angle with the drive link, placing them in toggle and creating a rigid structure to hold the switch securely in a closed position. The structure is preferably configured such that the rotation of the cam plates is greatest when the motion of the blades is least at the end of the rotation of the drive shaft into the closed and locked position. Thus, the need for a latch to coordinate the blade position with the contact pressure clamping action is eliminated. The pressure between the blades is increased slightly before the blades are in a fully closed position, and are fully pressured at the point where the blades are in a completely closed position, allowing a high pressure wiping action which creates a cleaner contact surface. However, the pressure is released before substantial movement of the blades during opening, allowing opening to occur without increased force, and decreasing mechanical wear. The rise and dwell shape of the cams allows over travel after reaching full contact pressure, and thus eliminates the need for position adjustment. Also, the fixed rise of the cams allows for adjusting the tie bolts by tightening them solid with the cams unlocked, then backing off a specific amount, such as a sixth of a turn, eliminating the need to tighten by feel as with conventional switches.
Torsional springs are preferably provided at the drive shaft such that resistance is encountered when the drive shaft is rotated in either direction. Stops are provided to prevent rotation of the drive shaft past the fully open or fully locked positions.
By forming the switch in a fashion such that the blades can engage and disengage the terminals without pressure applied, yet allowing the cams to provide pressure gradually with engagement eliminates numerous problems.
The cams may be stamped plates. The pressure switch device has applications in circuit interrupters, disconnect devices, and numerous other applications.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.
REFERENCES:
patent: Re. 31634 (1984-07-01), Norby
patent: 2090474 (1937-08-01), Crabbs et al.
patent: 2347030 (1944-04-01), Crabbs
patent: 2546366 (1951-03-01), Lindae
patent: 3180963 (1965-04-01), Hales et al.
patent: 3593235 (1971-07-01), Nicol
patent: 3604300 (1971-09-01), Allison
patent: 3614362 (1971-10-01), Keranen
patent: 3624333 (1971-11-01), Schurr
patent: 3632936 (1972-01-01), Piber
patent: 3636286 (1972-01-01), Hults
patent: 3644793 (1972-02-01), Ilk
patent: 3646355 (1972-02-01), Ireland et al.
patent: 3680016 (1972-07-01), Becker et al.
patent: 3711669 (1973-01-01), Keranen
patent: 3720797 (1973-03-01), Gunn et al.
patent: 3726494 (1973-04-01), Flagg et al.
patent: 3740741 (1973-06-01), Jones
patent: 3742402 (1973-06-01), Nicol et al.
patent: 3742403 (1973-06-01), Nicol
patent: 3787654 (1974-01-01), Rys
patent: 3805115 (1974-04-01), Heckelman
patent: 3809840 (1974-05-01), Schurr
patent: 3838355 (1974-09-01), Papaieck
patent: 3875360 (1975-04-01), Rys
patent: 3876847 (1975-04-01), Dykes et al.
patent: 3879589 (1975-04-01), Rys
patent: 3881077 (1975-04-01), Piber
patent: 3891862 (1975-06-01), Clark
patent: 3895198 (1975-07-01), Piber
patent: 3919513 (1975-11-01), Phillips
patent: 3967132 (1976-06-01), Takamine
patent: 4001683 (1977-01-01), McNeilly
patent: 4002874 (1977-01-01), Brown
patent: 4041260 (1977-08-01), Swindler et al.
patent: 4110585 (1978-08-01), Brown
patent: 4121065 (1978-10-01), Woodard
patent: 4121069 (1978-10-01), Long
patent: 4154997 (1979-05-01), Grebner et al.
patent: 4166935 (1979-09-01), Norby
patent: 4177389 (1979-12-01), Schott
patent: 4218602 (1980-08-01), Creech
patent: 4267711 (1981-05-01), Kolze
patent: 433
Engel Edward I.
Ratliff Larry Gene
Golden Larry I.
Scott J. R.
Shrout Larry T.
Square D Company
Stacey David R.
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