US2438810A - Centrifugally operated switch - Google Patents

Description

March 30, 1948. LAMBERT 2,438,810

CENTRIFUGALLY OPERATED SWITCH Filed Feb. 24, 1944 ATTORNEYS Patented Mar. 30, 1948 CENTRIFUGALLY OPERATED SWITC Harry L. Lambert, Enfleld. N. Y., assignor, by mesnc assignments, to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Application February 24, 1944, Serial No. 523,877

13 Claims. (01. 200-40) This invention relates to switches, and more particularly to those switches which are controlled by centrifugal forces.

Switches 01 this type have a variety oi uses, such as to operate signals and various electrical controls and devices, and to control the speed of motors. There is a substantial commercial demand for small universal motors which will operate on either A. C. or D. C. current, but the speed of such motors varies with the load and iiuctua tions in voltage. Speed governors for such motors have been proposed, but they have been unsatisfactory because of their relatively large initial expense, the cost of maintenance, the space occupied, their inability to operate within sufiiciently close limits, and the relatively weak power at reduced speeds of the motors so com trolled.

An object of the invention is to improve, sim pliiy and increase the effectiveness and accuracy of centrifugally operated electric switches.

Another object of this invention is to provide an improved centriiugally operated switch which will require a minimum of servicing at= tention; which will be closed and opened within relatively close, accurate speed limits; with which the speed at which the switch opens or closes may be varied over a considerable range, in a simple manner and even while the switch is operating; and with which the contacts will be kept clean through use.

Another object of this invention is to provide an improved, centrifugally operated switch which may be set to operate at diflerent selected speeds within a possible range; which may be additionally and positively operated to open po sition and held open, irrespective of its speed of operation, even while the switch is rotating, and which, when released, will automatically return to the same condition, with respect to the speed at which it will operate, for which it was set before the switch was opened; with which the advjustment of the speed at which the switch opens and closes may be varied in a simplemanner while the switch is in use; and which is relatively simple, dependable, compact and inexpensive.

Still anotherobject of the invention is to pro= vide an improved, centrii'ugally operated switch in which the circuit controlling contacts may be kept clean and eflective in use, in a very simple and effective manner.

Other objects and advantages will be apparent from the following description of an embodiment oi the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

7 Fig. 1 is a side elevation of a small electric motor of the universal type, having applied thereto a centriiugally operated switch constructed in accordance with this invention, with the switch in this illustration connected to control the speed of the motor which operates it; 4

Fig. 2 is a transverse sectional elevation of the motor and a portion of the switch shown in Fig. l, the section being taken approximately along the line 2-2 of Fig. 1; and

Fig. 8 is a sectional elevation through por tion of the device to show the manner in which the abutment may be shifted to open or close the switch, whether the motor is operating or is idle, and to indicate more clearly the construction by which the contacts are kept clean in use.

The invention is in the nature of an improvement upon the ceutrifugaliy operated switch disclosed and claimed in my copending application No. 506,646 filed October 18, 194:3.

In the illustrated embodiment of the invention, the improved switch includes a blocl: or element it of insulating material, somewhat ey lindrical in shape and fixed on a rotatable shaft ii for rotation therewith. This shaft it may be rotated from any suitable source of power, but in this particular illustration, the shaft ii is the armature shaft of an electric motor it of the universal type, which is a motor that operates on either A. C. or D. C. current, as desired. One end of the shaft ii is extended beyond the motor to support the clock iii of insulating material, and this block it) is removahly secured on the shaft extension in any suitable manner. Mounted on that end face of the block or element it which is nearest the motor are spaced, metal, annular collecting rings i3 and M which are concentric with one another and with the shaft ii. Suitable brushes it and 16 are carried by, but insulated from, the housing of the motor i2 and bear upon the collecting rings [3 and I4 so as to establish continuous electrical connections between the rings 83 and 14 with circuit wires ii and it while the motor is operating.

A flexible, ribbon-like spring strip 19 oi metal. such as spring steel, or brass, or similar resilient conducting material is disposed adjacent the opposite or outer end face of the block or element "I, with its ends extending toward one another and secured to that face of the block ill by screws 20. The screws pass through apertures may have a reduced end which extends through.

an aperture in the ring I4, with the end that passes through the ring l4 upset to prevent its removal from the ring. The clamping of the ends of strip 19 against a face of the block l prevents removal of the collecting ring l4 and the studs 2|, but the studs 2! are preferably snugly fitted in the apertures in the block It] so that they are not easily removed after assembly.

The screws 20 are disposed at approximately diametrically opposite sides of the axis of the rotation of the shaft II, and the intermediate portion of the strip 19 is arcuately bowed away from block I0 and extends approximately across the axis of the shaft ll, so that centrifugal forces acting on the strip [9 as it rotates with the block in will tend to flex and straighten out the bow in the intermediate portion of the strip, which straightening out will cause a movement, in a direction parallel to shaft ll, of that part of the intermediate portion which crosses the axis of the shaft II. Preferably, the intermediate portion 'of the strip I9 is arcuately bowed as at 22 from each end with a re-entrant portion 23 between the bowed portions where it crosses the axis of the shaft I I. This re-entrant portion 23 carries a contact 24 which normally engages with a second contact 25 that is carried by the block W approximately at the axis of rotation of the shaft ii. When the intermediate, bowed or looped portion of the strip i9 is somewhat straightened out, or flattened either manually or by centrifugal forces created by-rotation of the block in and strip i9, the re-entrant portion 23 will move endwise of the shaft ii in a drcction to carry its contact 24 away from the cOIltaCt 25. v The contact 25 is provided on a metal contact strip 23 which abuts approximately flat against the outer end face of block l0 and extends somewhat crosswise of the strip Ill, as shown clearly in Fig. 2. The ends of the strip 26 are secured by screws 21 to metal studs 21A that are carried by the block Ill and anchored to the other collector ring 13, in the same way that the screws 20 are secured to studs 2| that are siryiil-arly anchored to the collector ring M. This places the contact 25, through ring l3 and brush i5, electrically in circuit with wire H. The circuit wire l8, through the brush l6 and ring i4, is electrically connected to the strip i9 and through it to the contact 24.

Screws 28 are threaded into the outer end face of the block it beneath the intermediate portion of the strip 26, and each of these screws has a reduced outer end which passes through an aperture in the intermediate portion of the strip 26, so that the shoulder between the outer reduced end and the body of the screw 28 will abut against the underface of the strip 26. By turning the screws 28 in a direction tending to remove them from the block l0, they will, by their engagement against the underface of strip 26, bow or spring the intermediate portion of that strip in a direction toward the contact 24, so that more powerful forces will berequired to straighten out the strip i9 sufliciently to separate the contact 24 from the contact 25. In other words, a greater straightening outof the intermediate portion of thestrip I9 will be required before contact 24 will separate from contact 25. Similarly, when the screws 28 are threaded into the block ill, the strip 26 will be released and will spring toward the face of block Hi. This flexing of strip 26 varies the speed at which the centrifugal forces will be sufficient to separate contacts f 24 and 25.

A second, flexible, ribbon-like, spring strip 29 has its ends abutting face to face with the ends of the strip [9 and is secured to the block In by the same screws .20 which secure the ends of the strip iii to block In. The second strip 29 is convexly bowed with a large loop, as shown clearly in Fig. 1, without any re-entrant portion, and is also coupled to the strip l9 at the radially outermost parts of the intermediate portion of the strip l9. This coupling is conveniently established by clipping small weights39 to both springs l9 and 29 adjacentthe radiallyoutermost parts of both strips, where the strips abut. These weights 39 increase the centrifugal forces acting on the strip is for any speed and tending to straighten out the bowed or looped intermediate 7 portion, and thus increase the effectiveness of the centrifugal forces in tending to separate contacts 24 and 25. The weights arepreferably placed on the insides of the loop so that centrifugal forces cannot pull them loose from strips 19 and 29.

The motor I2 is secured upon a base 3| which has an upstanding arm or flange 32 that crosses,

36 which by engagement with opposite'sides of the arm 32 limit endwise, sliding movement of the bushing in aperture 33 t0 the extent permitted by the spaces between these shoulders and the adjacent faces of the arm 32. Threaded endwise through this bushing 34 is an abutment screw or member 31 having at its outer end an operating knob 38, and at its inner end a conical tip 39 which bears in a conical recess 46 provided in the second strip 29 approximately where it crosses the axis of the shaft H. The periphery of knob 38 is provided with peripherally spaced grooves, that run parallel to the axis of screw 31, and into one of which a spring detent 4| carried by the arm 32 maysnap when the knob is stopped in different positions. This knob may be turned to advance the conical end 39 toward or from the spring strip 29, and the spring detent M will hold the knob in the different adjusted positions.

Suitable means is provided for also shifting the bushing 34 in a direction to compress the'spring strip 29 sufficiently to cause separation of the contacts 24 and 25, and for this purpose, a bell crank lever 42 is pivoted at 43 on a bearing lug 44 carried by the upstanding arm 32. One arm of the bell crank 42 is forked to straddle the abutment screw 31 and abuts against an end face of the bushing 34, so that when the bell crank is rocked counter-clockwise in- Fig. 1, the forked end will cam the bushing 34 bodily to the right into the position shown in Fig. 3, and thus advance the abutment member or screw 37 a deflnite amount determined by the shoulder 36. This compresses the convex, intermediate portion of spring strip 29, which forces the radially outermost portions of this spring strip further outwardly and stretches the intermediate portion 22 of the spring strip 19 in the same direction the bell crank 42 is released, the resiliency of strip 29 will shift the screw 31 back until shoulder 35 engages arm 32, and this then restores the parts automatically to the same initial position that the screw 3'! occupied before the movement of the bell crank 42. The bell crank 42 may be operated to cause an opening or closing of the switch in any suitable manner, but for convenience, a chain 45 is shown connected to the bell crank. Obviously, other operating means for the bell crank and for holding it in its circuit opening position may be provided.

The'screw 37 which bears against the spring strip 28 is preferably disposed with its axis (shown by the dot and dash line 46 in Fig. 3). disposed parallel to but slightly offset from the axis of the shaft H (shown by the dot and dash line 41 in Fig. 3), so that the screw 31 and its conical tip 39 will be slightly eccentric to the axis of rotation of the strip 29. Since the conicaltip 39 runs in a recess 50, the recess 40 may also be slightly eccentric to shaftil, and thus as the strip .29 rotates, this eccentricity will cause'small free of oxide films or other agents that would interfere with the making of a good electrical contact when these contacts engage.

When the switch is used merely to operate a signal circuit, the wires ll and it are, of course, connected in the circuit to be controlled, but in r the example illustrated, the switch controls the speed of the motor i2 which operates it, and hence the wires l1 and i8 are shown as connected in series with the motor, so that opening of the circuit at the contacts 24 and 25 will open the circuit of the motor. An electrical condenser 48 of substantial size is connected across the conductors I1 and is for reducing radio interference due to the making and breaking of the circuit at the contacts 24 and 25, and also for the purpose of reducing arcing between those contacts; which arcing would cause pitting of the contact surfaces.

In the operation of the'lllustrated example of the invention, the circuit wires H and it are connected to a suitable source of commercial current, with the motor i2 in series in wire i8, and since the contacts 24 and-25 are normally in engagement with each other, a circuit will be established through the motor i2 and the shaft l I v will rotate. The block Ill and the springs i9 and 29 will also rotate with the shaft H, and the centrifugal forces acting upon both of the strips l9 and 29 will tend to cause them to elongate radially or to flatten out the bows or bends therein. The centrifugal forces so created are increased by those created through the presence of the weights 3!! which clip the two strips l9 and 29 together at their radially outermost points.

When the centrifugal forces tending to straighten out the strip iii are sumcient to overcome the resistance due tothe resilience of the parts is and 29, the re-entrant portion 23 will move in a direction away from'the contact 25 and separate contacts 24 and 25. When the circuit opens, the speed of the motor will fall and at the same time the centrifugal forces will decrease with this decreasing motor speed so that the resilience ofthe strips l9 and 2-8 will immediately return towards their former shapes and re-engage contact 24 with contact 25. This reestablishes the circuit to the motor and the motor again accelerates in-speed. The motor will, therefore, be held at a particular speed for which the switch is set.

When the bowed part of the strip 29 is flattened to different extents by turning of knob 33, it will tend to separate the radially outermost parts of the strips l9 and 29 in the same direction that the centrifugal forces tend to elongate or flatten these strips, so that the centrifugal forces necessary to complete the flattening and separate contacts 24 and 25 will be less than before the abutment screw 31 was adjusted to increase the flattening of strip 29. The speed at which the switch will open is, therefore-less as the knob 38 is turned to the right, or as the screw 31 is advanced to the right in Fig. 1. If one desires to. stop the motor, it is merely necessary to pull down on the chain 25 which will rock the bell crank d2 and shift bushing 34 to the right from the position shown in Fig. 1 to the position shown in Fig. 3, which flattens the strip 29 suiiiciently to carry the contact 24 out of engagement with contact 25. This opens the circuit of the motor i2 and holds it open.

If the conductors ill and i8 from the switch are not connected in series with the motor, but to a signal or other device to be controlled, this separation of the contacts 2d and 25, obtained by pulling the chain 65, will open the circuit through the conductors il and i3 and thus incapacitate the signal or other device controlled thereby. When the chain 45 is released, the resilience of strips 99 and 2% will return the bushing 34 to the position shown in Fig. 1, and since the abutment screw 32/ occupies the same relative position therein as before, the switch will be set to open at the same speed as before. Thus one may, by using the same switch, open or close the switch in the circuit it controls or vary the speed at which the switch will open under the action of centrifugal forces. The slight eccentricityhetween the conical tip 39 of the screw 3'! and the axis ofrotation of the spring strip 29 with shaft M will cause repeated wiping of the abutting surfaces of the contacts 24 and 25 and keep them clean.

It will be understood that various changes in the details, materials and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim as my invention:

1. A centrifugally operated switch comprising an element mounted for rotation about an axis, a flexible, ribbon-lika'sprlng strip anchored to said element for rotation therewith, said strip having a. portion thereof yieldingly urged, by the resiliency of the strip, away from the position into which it would be urged by centrifugal forces caused by said'rotation, but movable in a direction generally parallel to said axis, in opposition to the resiliency of said strip by the action of said .centrifugal forces, contact means engaged and strip and controlling the pressure exerted by said strip in opposition to centrifugal forces whereby the speed at which movement of said strip under centrifugal forces will causeengagement or disengagement of said contact means, may be predetermined, said last named means including an abutment disposed approximately at the axis of rotation of saidelement and non-rotatable with said element, and a member rotating with said element, engaging said abutment, and acting upon said spring strip in a direction to move said strip against its resiliency and lessen the centrifugal forces necessary to cause relative movement of said contacts whereby the setting of said abutment will determine the speed necessary to create centrifugal forces of a size that will cause relative movement of said contact means in an opening or closing directiom I 2. A centrifugallyoperated switch comprising an element mounted for rotation about an axis, a flexible, ribbon-like, spring strip anchored to said element for rotation therewith, said strip having a free portion yieldingly urged, by the resiliency of the strip, away from the position into which it would be urged by centrifugal forces caused by said rotation, but movable in a direction generally parallel to said axis, in opposition to the resiliency of said strip 'by the action of said centrifugal forces, contact means engaged and separated by said movement of said free portion of the strip, and means acting on said free portion of said strip and controlling the pressure exerted by said strip in opposition to centrifugal forces determined, said last named means including an whereby the speed at which movement of said strip under centrifugal forces will cause engagement or disengagement of saidcontact means, may be predetermined, said last named means including an abutment disposed approximately at the axis of rotation of said element and non-rm tatable with said element, and a second spring strip rotating with said element, engaging said abutment, and acting upon the first mentioned spring strip in a direction to move said strip against its resiliency and lessen the centrifugal forces necessary to cause relativev movement of said contacts whereby the setting of said abutment will determine the speed necessary to create centrifugal forces of a size that'will cause relative movement of said contact means in-an opening or closing direction, said abutment'and said second spring strip having interengaging surfaces slightly eccentric to the axis of rotation, whereby rotation of said second spring strip and the first mentioned spring strip relatively to said abutment will cause limited relative movement of said contact means in a direction crosswise of the axis of rotation.

3. A centrifugally operated switch comprising abutment disposed approximately at the axis of rotation of said element and non-rotatable with said element and a member rotating with said element, engaging said abutment, and acting upon said spring strip in a direction to move said strip against its resiliency and lessen the centrifugal forces necessary to cause relative movement of said contacts whereby the setting of said abutment will determine the speed necessary to create centrifugal forces of a size that will cause relative movement of said contact means in an opening or closing direction, means mounting said abutment for relative movement in a direction parallel to said axis of rotation, a support arrying said mounting means for limited movement in a direction parallel to said axis, and means for selectively shifting said mounting means, and with it said abutment in said support so as to carry said abutment rapidly between said limits of movement.

4. A centrifugally operated switch comprising a rotatable element, a flexible, ribbon-like, spring strip secured at both ends to said element at approximately diametrically opposite sides of the axis of rotation of said element, with an intermediate, free, bowed portion extendinggenerally across the axis of rotation; a contact carried by said element at approximately said axis of rotation, a ontact carried by said intermediate, bowed portion also at approximately said axis of rotation, said-contacts being arranged on that side of said strip which will cause their separation from each other in a direction parallel to said axis when the centrifugal force set up in said spring strip by its rotation is sufiicient to overcome the resiliency of the strip and move said intermediate portion in a direction parallel to said axis, spring means acting on said spring strip in a direction an element mounted for rotation about an axis, a

flexible ribbon-like string strip anchored to said element for rotation therewith,-said strip having a free portion yieldingly urged by the resiliency of the strip away from the position into which it would be urged by centrifugal forces caused by said rotation, but movable in a direction generally parallel to said axis, in opposition to the resiliency of said strip by the action of said cantrifugal forces, contact means engaged and separated by said movement of said free portion of the strip, means acting on said free portion of said strip and controlling the pressure exerted by said strip in opposition to centrifugal forces whereby the speed at which movement of said strip under centrifugal forces will cause engagement ordis-. engagement of said contact means, may be preto decrease the pressure of said strip in opposition to the centrifugal force, and an abutment acting on said spring means to determine the pressure exerted by said spring means on said strip, whereby the pressure which the centrifugal force acting on said strip must overcome in order to cause relative movement of said contacts through a straightening of the intermediate portion of strip. may be varied by moving said abutment to various predetermined position.

5. A centrifugally operated switch comprising an element mounted for rotation about an axis, a flexible, ribbon-like, spring strip secured at its ends to said element at approximately diametrically opposite sides of said axis-and having its intermediate portion free, re-entrant and bowed, whereby centrifugal forces acting on said strip when said strip and element rotate, will tend to straighten out said bowed and re-entrant portion and cause movement of said re-entrant portion in a direction parallel to the axis of said shaft, a contact carried by said re-entrant'portion, another contact carried by said element, both contacts being disposed approximately at said axis, a second flexible, ribbon-like, spring strip coupled to said first strip adjacent the anchored ends of said first strip and convexly bowed in its intermediate portion spaced from the re-entrant portion, and an abutment engaging with said bowed, intermediate portion of said second strip in proximity to said axis, by which said bowed intermediate portion may be flattened to selected extents, whereby by predetermining the position of said abutment in a direction along said axis cause separation and approach of said contacts 7 straighten out said bowed and re-entrant portion and cause movement of said re-entrant portion in a direction parallel to the axis of said shaft, a contact carried by said re-entrant portion, another contact carried by said element, both contacts being disposed approximately at said axis, a second flexible, ribbon-like, spring strip coupled to said first strip adjacent the anchored ends of said first strip and convexly bowed in its intermediate portion spacedfrom the reentrant portion, and an abutment engaging with said bowed, intermediate portion of said second strip in proximity to said axis, by which said bowed intermediate portion may be flattened to selected extents, whereby by predetermining the position of said abutment in a direction along said axis the speeds at which the centrifugal forces will cause separation and approach of said contacts may be varied, said abutment being selectivelyshifta'ble along said shaft axis to straighten said second strip to selected extents and, if shifted sufficiently, to separate said contacts.

7. A centrifugally operated switch comprising an element mounted for rotation about an axis, a flexible, ribbon-like, spring strip secured at its ends to said element at approximately diametrically opposite sides of said axis and having its whereby centrifugal forces acting on said strip when said strip and element rotate, will tend to straighten out said bowed and re-entrant portion intermediate portion free, re-entrant and bowed,

and cause movement of said re-entrant portion in a direction parallel to the axis of said shaft, a contact carried by said re-entrant portion, another contact carried by said element, both contacts being disposed approximately at said axis,.

a second flexible, ribbon-like, spring strip coupled to said first strip adjacent the anchored ends of said first strip and convexly bowed in its intermediate portion spaced from the re-entrant portion, a support, a member disposed approximately at said axis, mounted on said support and shiitable thereon in directions parallel to said axis to limited extents, an abutment adjustably mounted in said member for additional movement therein in a direction parallel to said axis and engaging-the bowed intermediateportion of said second strip, the resiliency of said second strip being suflicient to keep said member at one of its limits of movement, and means for quick- 1y shifting said member in the opposite direction to flatten the bowed part of said second strip and cause straightening of said intermediateportion of said first strip sufficiently to separate said contacts.

8. A centrifugally operated switch comprising an element mounted for rotation about an axis, a flexible, ribbon-like, spring strip secured at its ends to said element at approximately diametrically opposite sides of said axis and having its intermediate portion free, re-entrant and bowed,

whereby centrifugal forces acting on said strip when said strip and element rotate, will tend to straighten out said bowed and re-entrant por- 10 tion and cause movement of said re-entrant portion in a direction paralleito the axis of said shaft, a contact carried by said re-entrant portion, another contact carried by said element, both contacts being disposed approximately at said axis, a second flexible, ribbon-like, spring strip coupled to said first strip adjacent the an- ,chored ends of said first strip and convexly bowed in its intermediate portion spaced from the reentrant portion, a supporthaving an aperture approximately aligned with said shaft, a sleeve member slidable in said aperture in directions parallel to said shaft and having stops limiting said sliding movement in both directions, an

abutment member threaded lengthwise through said sleeve member and disposed in a position approximately parallel to said shaft and abutting at one end against the intermediate portion of said second strip to flatten said intermediate portion to extents depending upon the adjustment of said abutment member along said axis and means for bodily shifting said sleeve member endwise in said support to one limit of its movement so as to flatten said intermediate portion of said second strip sufliciently to cause a separation of said contacts by a straighten ng of the intermediate portion of said first strip, whereby when said sleeve member is released, the resiliency of the intermediate portion of said second strip will immediately return said sleeve member to its initial limit of movement with said abutment member in the same relative position alon said shaft.

9. A centrifugally operated switch, comprising an element mounted for rotation about an axis, a flexible, ribbon-like, spring strip secured at its ends to said element at approximately diametrically opposite sides of said axis and having its intermediate portion free, re-entrant and bowed,

whereby centrifugal forces acting on said strip when said strip and element rotate, will tend to straighten out said bowed and re-entrant por tion and cause movement of said re-entrant portion in a direction parallel to the axis of said shaft, a contact carried by said re-entrant portion, another contact carried by said element, both contacts being disposed approximately at said axis, a second flexible, ribbon-like, spring strip coupled to said first strip adjacent the anchored ends of said first strip and convexly bowed in its intermediate portion spaced from the reentrant portion, a support having an aperture approximately aligned in directions parallel to said shaft and having stops limiting said sliding movement in both directions, an abutment member threaded lengthwise through said sleeve member and disposed in a position approximately parallel to said shaft and abutting at one end against the intermediate portion of said second strip to flatten said intermediate portion to extents depending upon the adjustment of said abutment member along said axis and means for .bodily shifting said sleeve member endwise in said support to one, limit of its movement so as to flatten said intermediate portion of said second strip sufficiently to cause a separation of said contacts by a straightening of the intermediate portion of said first strip, whereby when said sleeve member is released, the resiliency of the intermediate portion of said second strip will immediately return said sleeve member to its initial limit of movement with said abutment mem ber in thesame relative position along said shaft,

'said abutment member and intermediate portion 11 portions in the direction along said shaft, bu slightly eccentric to said axis, whereby rotation of said strips relatively to said abutment member will cause a limited crosswise movement of said strips relatively to said axis, and therebya relative sldewise movement of said contacts to v keep the abutting surfaces of the contacts clean. 10. A centrifugally operated switch comprising an element mounted for rotation about an axis,

1 a flexible, ribbon-like, spring strip anchored to said element for rotation therewith, said strip having a portion extending approximately across said axis and urged, by the resiliency of the strip, in a direction approximately parallel to said axis and away from that position towards which it may be moved by centrifugal forces created by its rotation about said axis, contact means closed and opened by said movement of said portion of the, strip during rotation of said element, and means for resiliently urging said strip towards its said position in aid of centrifugal forces,

' whereby the speed at which said forces will operate said contact means may be predetermined by the extent of said resilient urging.

11. A centrifugally operated switch comprisins anfelement mounted for rotation about an axis, a flexible, ribbon-like, spring strip anchored to said element for rotation therewith, said strip having a free portion extending approximately across said axis and urged, by the resiliency of the strip, in a direction approximately parallel to said axis and away from that position towards which it may be moved by centrifugal forces created by its rotation about said axis, contact means closed and opened by said movement" of said free portion of the strip during rotation of said element, and means for resiliently urging I said strip towards its said position in aid of centrifugal forces, whereby the speed at which said forces will operate said contact means may be predetermined by the extent of said resilient urging, said resilient urging means including a mg corresponding ends secured face to face and to said element at opposite sides of said axis,

with the intermediate portions of both first ex- 55 tending radially away from said axis adjacent both of its anchored ends, and then bowed in a direction generallyalong said axis, and approximately crossing said axis, the intermediate free portions of one of said strips having a re-entrant portion adjacent said axis'and spaced from the corresponding free, bowed portion of the other strip, a contact carried by said re-entrant portion, a second contact toward and from which said first contact moves as said one strip straightens its bowed portions under centrifugal forces created in saidstrips by their rotation. and means acting against the bowed free portion of the other of said strips for flattening it and, thereby flattening said intermediate bowed portion of said one strip to reduce the speed necessary to create centrifugal forces that will cause relative movement of said contacts along said axis.

13. A centrifugally operated switch comprising an element mountedfor rotation about an axis, a contact mounted on said element, a flexible, ribbon-like, spring strip secured at its ends to said element at approximately opposite sides of said axis and having a bowed intermediate portion extending across said axis, a contact secured to theintermediate portion of said spring strip which may engage with and separate from the first-mentioned contact when the centrifugal forces acting on. said strip during its rotation at different speeds causes straightening of the bowed intermediate portion to different extents to cause relative axial movement between said contacts, selectively adjustable means continuously acting on said strip to control the pressure exerted by said strip in opposition to said centrifugal forces thereby determining the speed at which separation of said contacts due to said centrifugal forces will occur, means to adjust said control means, and means to impart additional movement to the control means to cause said contacts to be separated irrespective of the speed of rotation of said element.

- HARRY L. LAMBERT.

REFERENGIES CHTIED The following references are of record in the file of this patent:

Sweden May 26, 1924

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