US2678570A - Mechanism for operating electric switches - Google Patents

Description

May 18, 1954 Filed May 31, 1951 v w. A. BLACK ETAL MECHANISM FOR OPERATING ELECTRIC SWITCHES 2 Sheets-Sheet 1 qnHid (fl- Yblack CA ilk. v no le (Aw-romQY-X May 18, 1954 w. A. BLACK ETAL MECHANISM FOR OPERATING ELECTRIC SWITCHES Filed May 51, 1951 2 Sheets-Sheet 2 Nv'amwoYaA/ mmo 04.61am

CA 7%. Doole v of 35 a cfl-r-ronms f Patented May 18, 1954 TENT OFFICE MECHANISM FOR OPERATING ELECTRIC SWITCHES William A. Black, Montclair, N. J and Arthur B. Poole, .Harwinton, Conn, assignors to Haydon Manufacturing Company, Inc.,

Torrington,

Conn, a corporation of Connecticut Application May 31, 1951, Serial No. 229,158

1 Claim.

The present invention relates to clock actuated switches and more particularly to a mechanism for obtaining snap action from a continuously running clock train.

It is an object of the present invention to provide a snap action mechanism for driving multicontact electric switches which is more simple and compact in construction, more positive in operation, and lower in cost than preceding mechanisms of the same general type.

It is a more detailed object to provide an improved step-by-step snap action mechanism in which friction is reduced to a minimum, which is proof against faulty operation as a result of severe shock and vibration, and in which synchronism between clock and switch is absolutely assured.

Other objects and advantages of the invention will become apparent as the discussion proceeds and upon reference to the drawings, in which,

Figure 1 is an exploded view of the mechanism embodying the present invention.

Fig. 2 is a vertical section looking edgewise at the mechanism with the parts assembled.

Fig. 3 shows a typical multi-contact cam switch arrangement suitable for use with the mechanismof Figures 1 and 2.

Fig. 4 is a stop motion view at the beginning of a cycle of operation.

Fig. 5 is a stop motion view at the releasing point of the cycle.

Fig. 6 shows the.mechanismimmediately upon release.

While the invention is susceptible of various modifications and alternative constructions and uses, there is shown in the drawings only one embodiment of the invention. Itis to be understood, however, that it is not intended to limit the invention by such disclosure and the aim is to cover all modifications and alternativeconstructions and. uses falling within the spirit and scope of the invention as expressed in the appended claim.

Referring to the drawings, the snap mechanism is included in a housing [0, which is generally cup-shaped and which has a circular mounting flange l l. The mounting flange is fastened to a mounting plate l2 having an aperture l3. Extending through the aperture is an input shaft l5 which carries at its end an input or drive pinion [6. The shaft is connected to the driving train of a synchronous clock motor (not shown).

, At the other side of the housing 10 is an output pinion I 1 which ispartially enclosedin a shield I 8. As will be covered in greater detail as the discussion proceeds, the output pinion I7 is advanced intermittently and with a snap-action upon continuous driving of the input pinion. Such intermittent action is employed to operate a switch mechanism generally indicated at (Fig. 3) which is connected to the pinion H by means of a gear train 2|. The switch 20 may be of a conventional type in which the switch blades 222:i are raised and lowered by cams 25-41. Since the cam drive takes place rapidly and with a snap action the switch contacts will be operated correspondingly quickly, thereby reducing arcing at the contacts and greatly increasing contact life as well as improving the accuracy of the timing. The present mechanism is especially applicable to switches employed in automatic washers for controlling the washing, rinsing and centrifugal drying cycles.

Referring now to the snap-action mechanism in greater detail, it will be seen that it includes a cam gear 30, a ratchet mechanism 3| and a circular ratch 32. The ratchet mechanism is so constructed that rotation of the cam gear causes unlocking of the ratchet with the result that the ratchet mechanism is advanced periodically from one ratchet tooth to the next upon passage of time.

The ratchet mechanism 3| includes a pawl member which is slidably mounted in a pawl carrier 4 I. For this purpose, the pawl carrier has a transversely extending body 42 and two inward- 1y turned ends 43, ,44, making the carrier of generally U-shape. In the ends 43, 44, are guides in the form of rectangular openings 45, 46, which are alined with one another. The pawl member 40 has a body indicated at having outwardly extending arms 5|, 52, which are dimensioned to be slidably received in the openings 45, 46, of the carrier. The body of the pawl member is of lesser width than the carrier so that the pawl member is free to slide back and forth in the carrier. The path of movement is preferably diametrical with respect to the axis of rotation of the carrier.

At the outer end of the arm 52 is a radially exw tending tooth or pawl 53. The latter is of such size as to readily engage the ratchet teeth 6i-8 which are internally arranged on the ratch 32.

In carrying out the invention novel means are provided for withdrawing the pawl 53 from a given tooth upon rotation of the cam gear 39 and for simultaneously storing up energy so that the pawl may be snapped over to the next tooth in the series. For this purpose the cam gear 3!} includes cam members .ll, 12. These cam members are spaced apart on the gear 30 and are preferably formed as an axial extension of two diametrically arranged gear teeth. For the purpose of cooperating with the cam members ll, 12 the pawl member 40 includes a curved internal cam surface 13. Such surface is so formed as to produce retraction of pawl 53 when the gear so is rotated, as will be covered in detail.

The cam surface 13 is preferably formed as one wall of a D-shaped opening indicated at 14. For the purpose of storing energy for the snap action a spring '55 is interposed between the cam gear 30 and the pawl carrier 41.. This spring 55 includes radially extending ends 16, H, the end I! being received in a slot 18 in the cam gear while the end it engages an inwardly turned hook 'or abutment 12s on the carrier 42. Both the cam gear 30 and the spring it are loosely slipped over a shaft 19, which shaft is rigidly fastened to the pawl carrier ll.

When the device is assembled as shown in Fig. 2, it will be seen that all of the parts are compactly nested together so that the total thickness of the mechanism may be .made little more than the thickness of a pocket watch. The cam members H, '12 are received in the opening 14 in the pawl member and the pawl member itself is mounted within the pawl carrier 41, with the pawl 53 lying in the plane of the ratchet teeth 61-68.

The operation of the assembled device will be apparent upon reference to Figures 4, 5 and 6. Fig. 4 is a stop motion view showing the initial condition of the ratchet mechanism. The pawl 53 is engaged with the ratchet tooth El and the cam members H, 112 are symmetrically arranged with respect to the cam surface '13. The cam surface '13 is of shallow arcuate shape and is di mensioned to accommodate the cam members 1 i, 12 when such cam members are arranged crosswise therein and with the pawl member extended for engagement with a ratchet tooth. The cam surface 13 is formed by two intersecting arcs with centers of curvature at 73a and 130. As shown in Fig. 4, these centers 73a and E30 lie above the axis of rotation of the'cam members H, 1.2, so that the cam members rotate about an axis that is eccentric with respect to the curvature of said cam surface.

The effect of this arrangement will be made clear upon reference to Fig. 5, which shows the position of the members after a certain amount of counterclockwise movement of the cam gear Be. It will be seen in this figure that the cam member II has moved downwardly against the cam surface 13 with a wiping action. During such action the radius of the cam surface '13 relative to the center'of the shaft 79 becomes less and less, and continued movement of the cam gear results in the application of force as indicateol at 13a and the camming of the pawl member it to the left as viewed in Fig. 5.

During the time that such movement is taking place the cam member i2 moves upwardly along the right-hand portion of the cam surface 13, thereby permitting the pawl member 0 to move slowly to the left. However, it will be noted that the cam member '12 remains in contact with the cam surface l3 as it moves upwardly, thereby preventing the pawl member from being jarred into its fully disengaged position (to the left) as a result of shock and vibration. In brief, the pawl member islocked with respect to: the tooth 61 and the'only thing which can unlock :it is full retraction by the .cam gear. As a result, premapractically all of the energy supplied to the meshan'ism by the clock may be usefully employed to operate the switch and a minimum of energy is wasted in overcoming friction.

During counterclockwise rotation of the cam gear 30, the spring 15, one end of which is engaged with the gear 30, is tensioned, thereby applying a progressively increasing torque to the pawl carrier 41. This torque is in such direction as to urge the pawl carrier in a clockwise or advancing direction. The carrier is, however, locked in place until the cam gear turns through a predetermined angle. This condition is shown in Fig. 5 where the pawl 53 is almostfully retracted, enabling the spring to snap the entire mechanism over to the next tooth 62.

The snap action is illustrated in Fig. 6, where it will be seen that the pawl 53 is moving in the direction of the arrow into the dotted position in which the pawl is fully seated against the tooth 52. During the snap action practically all of the energy previously stored in the spring i5 is utilized to advance the gear train 21 associated with the switch 29. To insure accurate timing, the switch cams 25-21 are preferably so arranged that drop-on of the contacts takes place at the mid-point of the advancing step.

During the instant of snap-over the cam members 7!, l2 remain substantially fixed in position and the pawl member rotates relative to these two cam members. During such rotation the right-hand portion of the cam surface "53 wipes against the cam member 12. This applies .a pressure against the cam surface E3, as indicated by the arrow 73b, which, as will be seen in Fig. 6, has a large component tending to force the cam member to the right (outwardly) for engagement with the next tooth 6-2. The wiping action of the cam surface against the cam member 12 insures that the pawl will be moved outwardly in ample time to engage the next tooth. Thus, there is no possibility of missing a tooth and synchronism of the clock switch is accurately maintained.

Upon'further rotation of the cam gear 30 the entire cycle of operations outlined above is repeated and the pawl 53 is caused to clear the tooth 62, coming to rest seated against the tooth $3. The cycle is repeated for each of the successive teeth.

The pawl member ti) and the ratch 32 are preferably constructed of metal which may be hardened so that there is substantially no wear even after many thousands of cyclesof operation. Each of these pieces may be made of a simple and inexpensive stamping. The pawl carrier 4| may also be a metal stamping, the blank being punched prior to inturning the ends thereof. The cam gear 36 may be simply constructed by employing an extra wide gear and then simply milling off the teeth on two opposite sides to leave only two teeth 1|, I2, which serve as the cam members.

The ratch 32 is pressed into the housing l0, being received, on a suitable internal rim or J shoulder. If desired, the circular ratch may be locked in place by forming a groove 32a in the periphery thereof, which registers with raised internal ridge 10a on the housing II).

From the foregoing it will be seen that the entire mechanism requires no parts which are special or diificult to fabricate. It may be constructed of simple stampings and with a minimum of milling or cutting operations. Operation is positive, the intermittent advancing torque being limited only by the strength of the spring '15 which in turn is limited by the torque available from the clock train. Such torque need not be great, however, since the energy which is stored up in the spring over a long period is released suddenly and with great force during a very short period. Further, since the moving parts are light in weight and symmetrically arranged and since the angular step is small (only 45), operation is much quieter than in snap mechanism previously employed. In spite of its small size, it has been found that the mechanism is capable of driving large and relatively heavy switch mechanisms.

What is claimed is:

A device for converting rotary motion to reciprocating motion including a housing, a shaft supported in said housing, a driven cam gear rotatably mounted on said shaft, said cam gear having a pair of cam abutments in the form of axially extended gear teeth on opposite sides of said cam gear, a member supported in said housing for reciprocable movement, a curved internal cam surface on said member engaged by one of said cam abutments during rotation of said cam gear to move said member linearly, and a second curved internal cam surface on said member engaged by the other of said cam abutments to lock said member against premature movement due to shock or vibration.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 594,260 Mead Nov. 23, 1897 610,129 Ericson Aug. 30, 1898 854,688 Brown May 21, 1907 1,100,515 Anderson June 16, 1914 1,369,445 Kruse Feb. 22, 1921 1,479,970 Leppert Jan. 8, 1924 2,386,048 Harkness Oct. 2, 1945 2,448,164 Woditsch Aug. 31, 1948 FOREIGN PATENTS Number Country Date 509,558 Germany Nov. 18, 1930 596,002 Great Britain Dec. 24, 1947

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