US3126458A - Bowen - Google Patents

Description

March 24, 1964 'r. BOWEN 3,126,458

PERIODICALLY OPERATED ELECTRIC SWITCHES FOR REGULATING THE RATE OF SUPPLY OF POWER TO DIFFERENT CIRCUITS 2 Sheets-Sheet 1 Filed Aug. 22, 1960 March 1964 T. BOWEN 3,126,458

PERIODICALLY OPERATED ELECTRIC SWITCHES FOR REGULATING THE RATE OF SUPPLY OF POWER TO DIFFERENT CIRCUITS 2 Sheets-Sheet 2 Filed Aug. 22, 1960 United States Patent 3,126,458 PERIODICALLY OPERATED ELECTRIC SWITCHES FOR REGULATING THE RATE OF SUPPLY OF POWER TO DIFFERENT CIRCUITS Tom Bowen, Hove, England, assignor to Smiths America Corporation, Lakeland, Fla. Filed Aug. 22, 1960, Scr. No. 51,007 Claims priority, application Great Britain Aug. 21, 1959 3 Claims. (Cl. 200-27) This invention relates to periodically operated electric switches for regulating the rate at which power is supplied to different circuits. Such switches are sometimes used, for example, in the control of electric cooking devices, such as boiling rings when the average input, and hence the heat generated, is adjusted by varying the proportion of each period of oscillation during which the switch is closed.

It is one object of the invention to provide a simple arrangement whereby all the switches may be actuated by the same means and may be independently adjusted so as to operate over different portions of each period of oscillation.

According to this invention a combination of multiple adjustable periodically operated switches for controlling different circuits comprises a number of pairs of contacts, a motor, an actuating member arranged to be reciprocated or oscillated by said motor and having a number of abutments or the like spaced apart thereon and arranged to actuate respectively contacts in different pairs of contacts, separate adjusting means associated with each pair of contacts and arranged either to move one contact or both contacts relative to the abutment in the direction of the latters movement so that during one stroke of the reciprocation or oscillation of the abutment the contacts will be brought together after predetermined movement of the abutment whereby the time in which they remain in contact during each reciprocation or oscillation may be varied.

In one arrangement according to the invention one contact in each pair is arranged to be engaged by one of the abutments on said member and means are provided for imparting adjusting movement to the other contact of the pair in the direction of movement of the associated abutment.

The two contacts in each pair may be mounted on or comprise two spring blades each anchored at one end so that the blades may resiliently yield in the direction of movement of said abutment, one of which blades is arranged to be engaged by an abutment and the second of which blades is arranged to be engaged by an adjusting element.

The resilience of the blades may tend to maintain them together and the second of which blades may be arranged on the opposite side of the first said blade to the abutment which engages the first blade so that adjustment of the second blade away from the abutment also adjusts it away from the first blade.

Alternatively the second blade may be engaged by the adjusting means which is arranged on the same side of the first blade as the abutment and the adjustment of the second blade away from the abutment also moves the first blade in that direction maintaining the contacts in engagement.

Each adjusting element may comprise a rotatable cam or eccentric secured to a setting spindle provided with a manipulating knob.

Each contact blade may be of the kind described in British patent specification No. 40,772/58 in which an L-shaped or J-shaped blank has the part at the junction between the two limbs bent in spiral fashion and the shorter limb is folded to provided a rigid stem having Patented Mar. 24, 1964 "ice a tab at its extremity by which the blade is fixed to a mounting. One of the blades in each pair is of a greater length than the corresponding limb of the other blade so as to project beyond it and the adjusting cam or eccentric is arranged to engage the projecting portion.

The end of the longer of the two blades may be cranked so as to be disposed at a greater distance than the remainder from the shorter blade. The reciprocating member may comprise a bar of insulating material one edge of which is formed a number of gaps spaced apart along it one for each pair of contacts and which bar is arranged in a guideway so that it extends across the blades with a pair of blades in each gap, the width of each gap being slightly greater than the spacing apart of the blades and the projecting end of the longer blade of each blade extending clear of the bar.

The end of the bar may be provided with a roller which engages the periphery of an eccentric continuously rotated by suitable means, most conveniently an electric motor, at a speed of a few revolutions per minute.

The throw of the eccentric is rather less than the maximum spacing apart of the blades.

Similarly the throw of the adjusting cam may be equal to the maximum spacing apart of the contacts or preferably slightly less.

The edge of each gap nearer the actuating eccentric thus constitutes the aforesaid abutment.

The various lugs to which the contacts are anchored may all be formed integrally with one base member on which the adjusting cams are mounted.

If an electric motor is used to drive the actuating eccentric, it is most conveniently a synchronous motor, which can then also be utilized to drive time-indicating and/ or controlled mechanism associated with the cooker.

By rotating the adjusting cam to bring the longer blade towards the shorter the time during which the contacts remain in engagement during one stroke of the reciprocation of the bar will be increased whereas by rotating the adjusting cam so that the blades may be as far apart as possible they may remain out of engagement for the whole reciprocation.

In order to reduce the load on the motor each adjusting means also co-operates with the blades engaged by the abutments, in such a manner as to withdraw it completely from contact with the abutment in the Zero input condition.

The following is a description of two embodiments of the invention suitable for use with an electric cooker having a number of hot plates and an oven heater, the temperatures of which may require to be independently varied, reference being made to the accompanying drawings in which:

FIGURE 1 is a plan view of the assemblage certain parts of which are cut away and other parts shown in section;

FIGURE 2 is an elevation of the arrangement shown in FIGURE 1 looking from the top of that figure, and

FIGURE 3 is a diagrammatic perspective view of an alternative arrangement.

The assemblage shown in FIGURES 1 and 2 comprises a number of switch units indicated generally at 10, 11, 12 and 13 and which are mounted side by side on a frame work 14. Mounted also on framework 14 is a constant speed motor 15 which actuates the switch mechanism and also comprises a time control mechanism for switching on and off a cooker oven.

Each switch unit comprises a casing having a front wall 16, a rear wall #18 formed from insulating material, and spafiing members 17 connected between the front and rear wa s.

Each switch unit also comprises a spindle 19 which is rotatable in bearings in the walls 16 and 18, and moulded onto the spindle is a cam which is formed with two cam tracks 21 and 22. The cam has a hollow boss 9' within which is located a spring 8 encircling the spindle 19 and abutting the front Wall 16 at one end and a shoulder on the cam at the other end; The spindle is provided with grooves in which are located split rings 7 for locating it against axial movement in relation to the front and back walls. The outer face of the hub portion 9 is provided with two axially extending slots 6 and which are circumferentially spaced apart and engageable by a spring detent 4 fixed to the spacing members 17. {1" he cam track 21 engages a contact blade 23 and the cam track 22 engages a contact blade 24. Each contact blade is formed in the manner described in the specification of British patent application No. 40,772/58 (899,966) in that it is provided with a, spirally wound portion 25 from which extends a tab 26. It will be seen that the contact blade 24 is on the, same side of the contact blade 23 as the cam track 22.

The tab 26 for the blade 24 is secured by rivets 27 to a holder 28 and the tab 26 for the blade 23 is secured by rivets 27 to a holder 29. The holder 2% is provided with a tag 30 which extends up through a slot in the rear insulating wall 18 in which it is a tight fit and has a part of it slit and bent over at 31 so as to hold it securely in the insulating back wall. Similarly the holder 29 for the blade 23 is provided with a tag 32 which extends through a slot in the rear insulating wall 18 and has a portion 31 bent over to hold it securely in position.

As will be seen from FIGURE 2 each contact blade 23 is of greater length than its companion contact blade 24 and extends into the path of movement of an abutment 33' which is in the form of a set screw in a threaded hole in a lug 34 formed on an insulating bar 35.

The bar 35 is slidably mounted in guideways 36 secured to brackets 37 fixed to the framework 14. The bar 35 has fixed to one end thereof a cam follower 38 having a V-shaped projection which engages a heartshaped cam 33? driven by the motor 15. The two cam tracks 21 and. 22 are so shaped and relatively disposed that should the setting spindle 19 be rotated into a position as shown in the second unit from the left of FIGURE 1 the cam track 21 forces the blade 23 against the action of the resilient spiral portion 25 so that the contacts 40', 41 on the two blades are the maximum distance apart. With this position the detent 4 holds the cam in this position and the extremity of the blade 23 is thus so disposed in relation to the abutment 33 that the abutment never comes into contact with it, thus this particular switch is maintained out of operation. It will be appreciated that'when the switches are in this permanently off position the bar. 35 is moved by the cam 39 its maximum distance tothe right and remains there and no load is placed on the constant-speed motor 15 by the switch assemblage.

Assuming the spindle is rotated counter-clockwise so as to move the cam tracks 21, 22 from the position shown in the second unit from the left to a position shown in the right hand unit, the blade 23 will have moved back by reason of its resilience towards the blade 24 and the contacts 40, 41 on the two blades would be brought into engagement. Assuming the bar 35 is then moved to the right, the contacts are broken and will not come into engagement until the bar again moves to the left and thus the circuit to which the contact blades are connected will only be established for a very short period during each oscillation of the bar. If the cam tracks are rotated still further counter-clockwise the blade 24 will be forced to the right carrying with it the blade 23, the extension of the blade 23 will be moved further away from the abutment. The contacts on the blade will not be opened until the bar 35 has been moved some distance to the right. Thus the circuit will remain established for a longer period.

If the cam tracks 21, 22 are rotated until the maximum 4 radius of the cam track 22 engages the blade 24, the blades 24 and 23 will be moved together the maximum distance away from the operating abutment and the ci-rcuit will remain permanently established, the detent 4 engaging in the slot 5 and holding the cam 20 in this position.

lt is found that if the separating speed of the contacts is less than about .020 inch per second an undesirable amount of interference may occur in radio and television apparatus, whereas if a separation speed of greater than .020 per second is used the interference is reduced to a tolerable level. The speed of the motor and the dimensions of the parts are chosen to achieve the right speed of movement.

In the arrangement shown in FIGURE 3 a number of pairs of contact blades 42, 43, each formed in the manner described in specification No. 40,772/ 58, have their tab portions 44, 45 fixed on opposite sides of a lug 47 on a supporting base '48. Thus the base 48 is provided with a number of such lugs 47, spaced apart along its length.

The contact blades are long enough to extend beyond the ends of the lugs and the contact blade 43 is cranked to provide an extension 49 projecting beyond the extremity of the contact blade 42.

Mounted to reciprocate in guideways 50 on the supporting base 48 is an insulating switch operating bar 51 which is provided on its under edge with a number of cut away portions 52 which are of greater width than the normal spacing apart of the contact blades 42, 43.

Mounted at one end of the operating bar is a roller 54, which is engageable by an eccentric 55 fixed to a spindle 56 mounted in a bearing 63 on the supporting base 48. The spindle 56 is driven through suitable transmissions from a constant-speed motor (not shown) which also drives a time control device and a main time switch for the cooker oven.

Mounted on the base 48 opposite the extension 49 of each switch contact blade 43 is a cam 57, the spindle 58 of which is mounted in a bearing 64 on the base 48 and is also-provided with a manipulating member 59. The left hand edges of the cut away portions 52 in the bar 51 correspond to the abutments referred to in the previous construction. When the cam 57 is in the position in which the smallest radius is in engagement with the extension 49 the contacts 63 and 61 on the blades 42, 43 will be in engagement with one another. Thus when the bar 51 is moved to the right urging the contact blade 42 also to the right the contacts will remain in engagement and thus a circuit is established during the whole of the reciprocation of the bar 51. If, on the other hand, the cam 57 is rotated into a position in which the blade 43 is moved a maximum distance away from the blade 42 then although the bar 51 is moved to the right moving with it the blade 42 the contacts will not come into engagement throughout the reciprocation of the bar 51 and the circuit will not be established. If the cam 57 is moved into any intermediate position the contact 60 on the blade 42 will come into engagement with the contact 61 on the other blade after the bar 51 has moved to a predetermined extent andthus the contacts will remain engaged during a part of the reciprocating cycle of the bar 51.

While there have been described above what are presently believed to be the preferred forms of the invention, variations thereof will be obvious to those skilled in the art and all such changes and variations which fall within the spirit of the invention are intended to be covered by the generic terms in the appended claims, which are variably worded to that end.

I claim:

1. An electric power regulator fora number of electric circuits, comprising a number of pairs of contacts, one pair for each circuit, a continuously running motor, an actuating member, means coupling said motor to said actuating member for imparting continuous cyclic movement to said actuating member, said actuating member being positioned to engage a first contact of each pair of contacts and to impart regularly repeated movement thereto, first adjusting means for adjusting the position of the other contact of each pair thereby to vary the times during which the contacts of a pair remain together and during which they are separated for each cycle of movement of said actuating member, and second adjusting means for selectively moving at least the first said contact of each said pair clear of said actuating member, said first adjusting means for each said pair of contacts comprising a first cam surface engageable with said other contact of said pair, said second adjusting means for each said pair of contacts comprising a second differently contoured cam surface engageable With the first said contact of said pair, and means for selectively varying the positions of said first and second cam surfaces in unison.

2. The combination as claimed in claim 1 in which detent means are provided for holding said one contact References Cited in the file of this patent UNITED STATES PATENTS 1,969,926 Eickhofi Aug. 14, 1934 2,294,573 Potter Sept. 1, 1942 2,503,082 Tuttle Apr. 4, 1950 2,816,184 Manning et al Dec. 10, 1957 2,849,551 Truesdale et al Aug. 26, 1958 2,941,051 Laviana June 14, 1960 3,028,472 Baird Apr. 3, 1962

Claims (1)

1. AN ELECTRIC POWER REGULATOR FOR A NUMBER OF ELECTRIC CIRCUITS, COMPRISING A NUMBER OF PAIRS OF CONTACTS, ONE PAIR FOR EACH CIRCUIT, A CONTINOUSLY RUNNING MOTOR, AN ACTUATING MEMBER, MEANS COUPLING SAID MOTOR TO SAID ACTUATING MEMBER FOR IMPARTING CONTINOUS CYCLIC MOVEMENT TO SAID ACTUATING MEMBER, SAID ACTUATING MEMBER BEING POSITIONED TO ENGAGE A FIRST CONTACT OF EACH PAIR OF CONTACTS AND TO IMPART REGULARLY REPEATED MOVEMENT THERETO, FIRST ADJUSTING MEANS FOR ADJUSTING THE POSITION OF THE OTHER CONTACT OF EACH PAIR THEREBY TO VARY THE TIMES DURING WHICH THE CONTACTS OF A PAIR REMAIN TOGETHER AND DURING WHICH THEY ARE SEPARATED FOR EACH CYCLE OF MOVEMENT OF SAID ACTUATING MEMBER, AND SECOND ADJUSTING MEANS FOR SELECTIVELY MOVING AT LEAST THE FIRST SAID CONTACT OF EACH SAID PAIR CLEAR OF SAID ACTUATING MEMBER, SAID FIRST ADJUSTING MEANS FOR EACH SAID PAIR OF CONTACTS COMPRISING A FIRST CAM SURFACE ENGAGEABLE WITH SAID OTHER CONTACT OF SAID PAIR, SAID SECOND ADJUSTING MEANS FOR EACH SAID PAIR OF CONTACTS COMPRISING A SECOND DIFFERENTLY CONTOURED CAM SURFACE ENGAGEABLE WITH THE FIRST SAID CONTACT OF SAID PAIR, AND MEANS FOR SELECTIVELY VARYING THE POSITIONS OF SAID FIRST AND SECOND CAM SURFACES IN UNISON.

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