US2412513A - Electric control device - Google Patents

Description

Dec. 10, 1946.

M. F. JONES ET AL ELECTRIC CONTROL DEVICE Filed Dec. 11, 1944 INVENTOR 2 Maur/ce f? Jones and fiue/ C. fines.

WITNESSES: I m k J 6% u...

BY 47 M8.

ATTORNEY Patented Dec. 10, 1946 UNITED STATES PATENT OFFICE ELECTRIC CQNTROL DEVICE Maurice F. Jones, Pittsburgh, and Ruel C. Jones, Forest Hills, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application December 11, 1944, Serial No. 567,636

6 Claims. 1

Our invention relates to electric control devices and has for its general object to provide control means which perform a control operation when the rate of acceleration or deceleration of a 1'0- tating machine part reaches a given value.

It is also an object of the invention to devise an acceleration or deceleration responsive switch which permits readily an adjustment, calibration or change of the critical value of the rate of speed change at which the switching operation is supposed to take place.

Another object, allied to the one just mentioned, is to render a switch, of the type referred to, capable of being separately adjusted for response to acceleration and deceleration, respectively, so that the corresponding critical values may be chosen differently if desired.

A further object of our invention is to provide a switch, as mentioned above, in which the response to rate of change in speed is due to the occurrence of relative motion between a driven rotatable member and a rotatable floating mass or flywheel member and wherein such relative IOtlOl'l is subject to frictional damping in order to prevent detrimental oscillatory or hunting effects.

In order to achieve these objects we design an electric contactor in accordance with the principles elucidated hereinafter with reference to the drawing, in which:

Figure 1 is a sectional top view of a switching apparatus according to the invention, the section being taken along the radial plane denoted in Fig. 2 by 1-1, and

Fig. 2 is an axial section through the same apparatus taken along the dihedral cut denoted in Fig. 1 by II-II,

The apparatus illustrated in the drawing is provided with a casing I which forms the supporting structure for the other parts and is pl vided at one side with a mounting flange The other side of easing is closed by a cover plate 3. A shaft 4 is revolvably mounted by means of ball bearings 5 and 6 in the flange portion and cover plate, respectively. The cover plate 3 carries an insulatin block 7 which supports three terminals 8, 9 and it, each forming a holder for a contact brush H, !2 and i3, respectively.

A hub M is keyed to shaft 4 and carries a disk E5 of insulating material. This disk is provided with an annular insulator !6. Three slip rings l7, l8 and I9 are mounted on the insulator it for engagement by the contact brushes 5 i, 2 and I3, respectively. Disk I5 is further equipped with a support 20 for two leaf spring contacts 2! and 22, Two further supports denoted by 23 and 24 are also mounted on disk 15 and carry two leaf spring contacts 25 and 2b, respectively. The four leaf spring contacts extend substantially in axial planes relative to the rotation of shaft 4, and con tacts 2i and 22 are axially spaced from the corresponding contacts 25 and 26, respectively. Contacts 2! and 22 are electrically connected with one of the slip rings, while contacts 25 and 26 are in connection with the remaining two slip rings, respectively.

The insulating disk l5 carries further a support 28 for an adjustable stop or calibrating mechanism which comprises a finger 29, a helical compression spring 38 and an adjusting screw 3|. One end of finger 29 rests normally against the support 28 and abuts against a projection of the support so as to be capable of pivotal motion in opposition to the biasing force of spring 30. This force can be adjusted by means of screw 3|. The other end of finger 29 is bent to an angular shape.

Another support 33 also mounted on disk l5 carries a finger 34, a helical compression spring 35 and an adjusting screw 35. One end of finger 34 is pivoted on support 33 while the other end, denoted by ill, is of angular shape. Support 33 and the parts attached thereto form a second stop or calibrating mechanism arranged symmetrically to the one described in the foregoing.

A flywheel 38 is revolvably mounted on shaft 4 by means of ball bearings 39 and cc. Two drive pins 4! and #2 project from flywheel 38 toward disk #5 and enter freely into elongated openings of disk 95, such as the opening denoted by 33 in Fig. 2. The above-mentioned angular ends 32 and 37 of fingers 29 and 34 are so located relative to pins 4! and 42, respectively, that each finger is normally in contact engagement with the adjacent pin. The contact surfaces of finger ends 32 and 37 extend at an angle to the radius which passes through the point of engagement between fin er and appertaining drive pin. Flyative to disk l5. wheel. 38 is normally held in a given position rel- Two supports 8 and 44, respectively, are firmly attached to the flywheel and carry each a barshaped and slotted bridging contact 45 and 46, respectively, consisting of silver or the like highly conductive material. The bridging contacts are located so that they enter between the adjacent pair of contact springs 2! and 25, or 22 and 26 when the flywheel rotates relative to disk I5.

It will be recognized from the foregoing that the shaft t with its hub l5 and the insulating disk 3 I5 with all parts attached thereto form a drivable member while the flywheel 38 and the appertaim'ng parts represent a floating member. The squared or flattened end c1 of shaft t serves to connect the drivable member with a rotating machine part whose acceleration or deceleration is intended to control the switching performance. When the. driven member is rotating at constant speed, the two stop mechanisms described in the foregoing hold the floating flywheel in midposiacceleration increases beyond the limit value,

the stop mechanism will yield so that one of the contact bars 35 or 36 enters between the adjacent pair of leaf spring contacts and closes a control circuit between two of the-contact terminals of the apparatus.

When the driven assembly decelerates, the same performance is obtained, except that now the other stop mechanism is operative so that the other contact bar closes a circuit between the appertaining two leaf spring contacts. In this .manner, an electrical control function can be performed by the apparatus in dependence upon the'occurrence of predetermined rates of accel- -eration and deceleration.

As explained in the foregoing, the two adjustable -stop mechanisms operate independently of each other, one being active in response to acceleration and the other responsive to deceleration. That is, only one of the two resilient stops here represented by the contact fingers 29 and 3 1 is in operation at a time. This has the advantage that the biasing force of each stop can be changed or calibrated independent of the other stop mechianism. Hence, the apparatus can be made to respond to one rate of acceleration and to another rate of deceleration, 01' it permits a very accurate-calibration of the two stop mechanisms if they are to become effective at the same rate of speed change regardless of the direction of the change.

Due to the fact that the contact surface of .each finger 29 and 3% lies at an angle to the radius of rotationwlth reference to the point of engagement between finger and appertaining drive pin, any relative motion between the driven member and the floating member will cause the contactsurface of the yielding finger to drag along the pin. This sliding motion produces friction which tends to dampen any oscillation apt to occur at sudden changes in rate of speed.

.The ends of the contact-bars and are wedgeshaped, so that they enter between the adjacent .spring contacts with aminimum increase in effort.

This-construction has further the-advantage that it provides a double break in the circuit. The friction occurring between the contact bar and the leaf springs provides additional-sliding friction which assists in the suppression of undesirable-oscillations. The sloping approach on the bridging contact has the advantage over a straight contact that contact pressure and friction decrease when the bar, under the biasing effect of the stop mechanisms, withdraws from the relative motion occurringbctween said the leaf spring contacts. This reduces the tendency of the contacts to stay closed at reduced rates of change in speed and, therefore, reduces the difference between the pickup and dropout rating of the switch. Another advantage of the contact structure is the fact that no flexible shunts are required.

The'elongated holesof the disk'lisuch as the hole denoted by 43 in Fig. 2, co-operate with the ends of the pins 4| and 42 in preventing an excessive deflection of the calibrating springs 3i] and 35. The pins are normally out of engagement with the edges of the holes, except when the relative motion between driven member and floatingmember is far in excess of the normally expected deflection. This allows freedom of movement over the required range but prevents detrimental overtravel.

Apparatus according to the invention are of advantage in control or regulating arrangements in which an electric control function is to be performed in dependence upon the occurrence of a given rate of speed change, or in cases where a machine is supposed to accelerate or decelerate at a high rate which, however, is intended not to exceed such a value as to incur -mechanical or electrical overloads. It will be understood that when only an acceleration responsive or only a decelerationresponsive control is required, only one of the stop mechanisms need be adjustable. It will also be obvious to those skilled in the art that various other modifications can be applied within the gist of ourinvention and without departing from the essential features of the invention as set forth in the claims annexed hereto.

We claim as our invention:

1. An electric control device comprising a rotatable drivable member, a floating mass'member coaxially rotatable relative to said drivable her, an adjustable spring device for imposing on said members a bias of selective magnitude for causing them to normally maintain agiven angular position relativeto each other, and iectric contact means having two co-cperative parts mounted on said two members respec lvely so as to perform a switching operation in response to two members when the rate of speed change of said drivable member exceeds a value determined by these-lected adjustmentof saidspring device.

2. An electric switch comprising a rotatable drivable member, a floating mass member coaxially rotatable relative to said drivable member, a resilient stop mechanism disposed between said twormembers for biasing them inone direction of relative rotation toward a position of rest relative to each other, an adjustable resilient stop mechanism also disposed between said two membersfor biasing them in the other direction tolard said position of rest, and-electric contact means having two co-operative parts mounted on said two members respectively so as to perform a rounding said pin for limiting the relative rotation of said members, and a calibratng mechanism mounted on said other member and having a resilient stop engaging said pin for biasing it in one direction or said relative rotation toward a position of rest relative to said one member, and electric contact means having two co-operative parts mounted on said two members respectively so a to v erform a switching operation in response to the relative motion occurring between said two members when the rate of speed change of said drivable member exceeds a value determined by the calibration of said mechanism.

4. An electric switch comprising a rotatable drivable member, a floating mass member coaxially rotatable relative to said drivable member, one of said members having a pin extending substantially in parallel to the axis of rotation and the other member having a resilient stop engaging said pin, said stop having an engaging surface extending at an angle to the radius of rotation at the point of engagement whereby frictional sliding motion is caused between surface and pin when said two members rotate relative to each other, and electric contact means having two cooperative parts mounted on said two members respectively so as to perform a switching operation in response to the relative motion occurring between said two members when the rate of speed change of said drivable member exceeds a given v value.

5. An electric switch comprising a rotatable drivable member, a floating mass member coaxially rotatable relative to said drivable member,

biasing means disposed between said members for causing them to normally assume a given angular position relative to each other, two insulated contacts resiliently mounted on one of said members in axially spaced relationship, and a bridging contact mounted on said other member so as to enter between and electrically bridge said spaced contacts under frictional sliding motion when said two members rotate relatively to each other due to the occurrence of an excessive rate of change in speed of said drivable member.

6. An electric switch comprising a rotatable drivable member, a floating mass member coaxially rotatable relative to said drivable member and having a pin extending substantially in parallel to the axis of rotation, said drivable member having a resilient stop for engaging said pin, said stop comprising a rigid support, a finger having one end pivoted on said support and the other end bent so as to form a surface for contacting said pin at an angle to the radius of rotation at the point of contact, a spring for biasing said pivoted finger end toward said support, and an adjusting screw for adjusting the biasing force of said spring, and electric contact means having two co-operative parts mounted on said two members respectively so as to perform a switching operation in response to the relative motion occurring between said two members when the rate of speed change of said drivable member exceeds a value determined by the setting of said adjusting screw.

MAURICE F. JONES. RUEL C. JONES.

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