US3818405A

US3818405A - Cam actuated multiple contact switching device

Info

Publication number: US3818405A
Application number: US00303535A
Authority: US
Inventors: H Randolph; Intosh H Mc; A Teichert
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1972-11-03
Filing date: 1972-11-03
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18

Abstract

The cam actuated multiple contact switching device of the present invention includes a housing having a plurality of pairs of upstanding flexible blades mounted thereon and carrying electrical contacts from their respective free ends and arranged to urge such contacts into contact with one another. The flexible blades are arranged in a row and have a cam shaft interposed between the blades of the respective pairs, such cam shaft including symmetrical cams disposed adjacent each pair of blades and being shiftable longitudinally to cause such cams to engage the respective blades to urge the respective pairs of contacts apart. Drive means is provided for shifting the cam shaft, and such cams may be arranged in staggered relationship with respect to the flexible blades so the contacts will be sequentially closed and opened as the shaft is shifted longitudinally in opposite directions.

Description

[ June 18, 1974 CAM ACTUATED MULTIPLE CONTACT SWTTCHTNG DEVICE Assignee:

Filed:

inventors: Hollis L. Randolph, Lakewood;

Harold A. McIntosh, South Pasadena; Allen Lee Teichert, Placentia, all of Calif.

Robertshaw Controls Company,

Richmond, Va.

Nov. 3, 1.972

Appl. No.: 303,535

US. Cl. 337/141, 200/153 LA, 335/141 Int. Cl. H0111 61/02 Field of Search 335/141, 126; 200/153 LA,

References Cited UNlTED STATES PATENTS 3,655,932 4/1972 Tabares et a1. 200/5 C Primary Examiner-Harold Broome Attorney, Agent, or Firm-Fulwider, Patton, Rieber, Lee & Utecht [57] ABSTRACT The cam actuated multiple contact switching device of the present invention includes a housing having a plurality of pairs of upstanding flexible blades mounted thereon and carrying electrical contacts from their respective free ends and arranged to urge such contacts into contact with one another. The flexible blades are arranged in a row and have a cam shaft interposed between the blades of the respective pairs, such cam shaft including symmetrical cams disposed adjacent each pair of blades and being shiftable longitudinally to cause such cams to engage the respective blades to urge the respective pairs of contacts apart. Drive means is provided for shifting the cam shaft, and such cams may be arranged in staggered relationship with respect to the flexible blades so the contacts will be sequentially closed and opened as the shaft is shifted longitudinally in opposite directions.

5 Claims, 9 Drawing Figures PATENTEB JUN I 8 I974 SHEET 2 OF 2 BACKGROUND OF THE INVENTION 1. Field of the Invention The cam actuated multiple contact switching device of the present invention relates to a device for use in applications where multiple switching is required for either sequential energization of controlled elements or for distributing the entire power requirement between a plurality of sets of contacts.

2. Description of the Prior Art Cam actuated switching devices have been proposed which include multiple contacts actuated by axially shiftable cam shafts. Devices of this type are shown in US. Pat. Nos. 3,250,881 and 1,926,419. However, such devices suffer the shortcoming that they are not automatically actuated and do not move pairs of contacts into contact with one another at equal and opposite rates of travel.

SUMMARY OF THE INVENTION The cam actuated multiple contact switching device of the present invention is characterized by a plurality of pairs of electrical contacts carried from respective pairs of resilient mounting means which are engaged by respective cams driven by a drive means to make and break such contacts upon shifting of such cams in one direction and the other. The cams are preferably symmetrical to cause the respective contacts of each pair of contacts to be brought together at equal rates of speed to thereby reduce bounce and consequent arcing between such contacts.

In certain applications, the spacing of the cams is staggered with respect to the spacing between the respective pairs of mounting means to thus cause the contacts to be sequentially closed as the cams are shifted. Further, a stepping device may be provided for storing energy upon actuation of the drive means and sudden incremental release thereof to cause the cams to be shifted rapidly and positively from one contact closing position to the next contact closing position.

The objects and advantages of the present invention will become apparent from a consideration of the following detailed description when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cam actuated multiple contact switching device embodying the present invention;

FIGS. 2, 3 and 4 are transverse sectional views, in enlarged scale, taken along the lines 22 of FIG. 1 and depicting an auxiliary switch in three different positions;

FIG. 5 is a transverse sectional view, in enlarged scale, taken along the line 5--5 of FIG. 1;

FIG. 6 is a longitudinal sectional view, in enlarged scale and partially broken away, taken along the line 6-6 of FIG. I and inverted; and

FIGS. 7, 8 and 9 are diagramatic views depicting operation of the cam actuated multiple contact switching device shown in FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 5, 6 and 7, the cam actuated multiple contact switching device of the present invention includes, generally, a housing 21 mounting a plurality of pairs of electrically conductive upstanding

resilient blades

23 and 25 which have respective pairs of

contacts

27 and 29 mounted from the free ends thereof. The

blades

23 and 25 project beyond the re

spective contacts

27 and 29 and receive therebetween a cam shaft, generally designated 31, which has a series of conically shaped axially spaced apart

cams

33, 35, 37, 39 and 41 formed thereon for selective disposition between the respective free ends of the pairs of

blades

23 and 25 to separate such blades sufficiently to disengage the respective pairs of

contacts

27 and 29 from one another. A drive device, generally designated 45, is connected with one end of the cam shaft 31 and is operative in response to actuation thereof to progressively shift such cam shaft 31 longitudinally to the left from the position shown in FIG. 7 to initiate sequential disengagement of the

cams

33 and 35 from their respective contact-carrying blades. Continued actuation of the drive means 45 will continue progressive movement of the cam shaft 31 to the left to sequentially disengage the remaining cams 37, 39 and 41 from the

respective blades

23 and 25 to thus progressively close all

contacts

27 and 29.

The housing 21 is in the form of a rectangular box 51 having an opening 53 formed in the top side thereof for receipt thereover of a plurality of separate electrically insulative switch bases 55. Referring to FIG. 5, the switch bases 55 have upwardly and outwardly angled wedge-shaped openings 57 formed therein, and the upper extremities of the

resilient blades

23 and 25 are bent to angle upwardly and outwardly to complement the slope of the wedge-shaped plugs 58 are inserted between the bases of the

blades

23 and 25 and serve to wedge the respective blades against the opposite walls of the opening 57, such wedges being bonded in place. The top extremity of the blades 23 and 2.5 projecting upwardly from the bases 55 form

respective plug prongs

61 and 63.

Referring to FIGS. 1 4, an auxiliary fan control switch, generally designated 67, is provided at the left hand end of the housing 2l (FIG. 1) and includes an electrically insulative base 69 having a pair of electrically conductive

resilient blades

71 and 73 mounted therefrom in spaced apart relationship and carrying respective

electrical contacts

75 and 76 from the free ends thereof. The

blades

71 and 73 project upwardly beyond the base 69 to form

plug prongs

72 and 74. Disposed intermediate the

blades

71 and 73 is a common electrically conductive blade 77 formed centrally with a flex joint 78 and having a pair of

contacts

79 and 81 carried from the opposite sides of the free ends thereof for selective engagement with the

respective contacts

75 and 76.

Referring to FIG. 2, a solenoid 83 is mounted from the base 69 and includes a plunger 85 coupled on its free end with the intermediate blade 77 to control positioning of such blade for selective positioning to complete a circuit through either the

contacts

75 or 76 when the cam shaft 31 is positioned for closure of such switch 67. The solenoid 83 has its coil connected in series with a collector switch 84. (FIG. 2)

Referring to FIG. 6, the cam shaft 31 is generally cylindrically shaped and the

individual cams

33, 35, 37, 39 and 41 are formed with respective frustrum-

shaped cam surfaces

93, 95, 97, 99 and 101 to engage the resilient blades disposed on the respective opposite sides thereof for uniform movement of such blades in the opposite directions when such cam shaft is shifted longitudinally. Referring to FIG. 7, it will be noted that the

cams

33, 35, 37, 39 and 41 are arranged in staggered relationship with respect to the respective pairs of

blades

23, and 71 and 73 to result in sequential making of the pairs of contacts carried thereby as the cam shaft is shifted from right to left.

The left hand extremity of the cam shaft 31, as viewed in FIG. 6, is formed with side-by side

annular retainer grooves

103, 105, 107, 109 and 111 for receipt of an indexing plunger 113 which is urged thereinto by means of a coil spring 114 to control incremental stepping of the shaft 31 to the various switch closing positrons.

Referring to FIG. 6, the drive mechanism 45 is mounted from the housing 21 by means of a mounting channel 116 and is in the form of a triangular movement multiplier linkage including an upwardly projecting lever 115 carried on its lower extremity from one end of the channel 116 by means of a pivot pin 117 and having its upper extremity engaged in a groove 119 formed in the right hand end of the cam shaft 31. Disposed at the opposite end of the channel 116 is a vertical link 121 carried on its bottom end from a pivot pin 123 and having a diagonal link 127 connected on one end with the upper extremity thereof by means of a pivot pin 129, the opposite end of such diagonal link 127 being connected with the lower extremity of the lever 115 by means of a pivot pin 129. Connected between the upper extremity of the lever 115 and the in termediate portion of the diagonal link 127 is a tension coil spring 133 which serves to normally maintain the upper extremity of such lever drawn to the left.

Still referring to FIGS. 6 and 7, a temperature responsive stainless steel rod 135 is connected on one end with a transverse flange 137 formed in the channel 116 and has its opposite end connected to the lower portion of the vertical link 121. The right hand end of the rod 135 is received in an externally threaded rod segment 141 which projects slideably through a bore 146 in the boss 137 and has a nut 145 screwed onto the extremity thereof for adjusting the setting of the cam shaft 31. Referring to FIG. 7, a pair of

heat motors

143 and 145 are wound on the opposite halves of the temperature sensitive rod 135 and are connected across the secondary coil of a transformer, generally designated 147, by means of parallel circuits including respective control switches 149 and 151.

In operation, the cam actuated multiple contact switching device of the present invention may conveni'ently be utilized to control a heating system such as an electrical furnace. In such installations, the respective heating elements (not shown) of the furnace are connected with the

respective plug prongs

61 and 63, such that progressive making of the

contacts

27 and 29 will progressively energize the respective heating elements. The two-speed blower of the electrical furnace may then have its first stage connected with the

plug prongs

72 and 80 with the second stage being connected with the

plug prongs

80 and 74. The solenoid 83 is then connected with the blower selector switch 84.

A thermostat incorporating the first and second stage switches 149 and 151 is then connected with the first and second

stage heat motors

143 and 145 and with the transformer 147.

When the thermostat senses a normal room temperature, the thermostat switches 149 and 151 will remain open thus leaving the

heat motors

143 and 145 deenergized and the temperature responsive rod 135 unheated thus restricting rotation to the left of the upper end of the vertical link 121, as viewed in FIG. 7, to restrain rotation to the left of the upper extremity of the lever arm 115 and maintain the cam shaft 31 in the position shown in FIG. 7. With the cam shaft 31 maintained in the position shown in FIG. 7, the respective cams 35, 37, 39 and 41 are maintained positioned between the respective free extremities of the

resilient blades

23 and 25 thus maintaining the respective

electrical contacts

27 and 29 spaced apart to maintain the furnace heating elements de-energized. Similarly, the cam 33 serves to maintain the blower contacts and 76 spaced apart thus maintaining the blower deenergized.

When the temperature sensed by the thermostat drops sufficiently to result in a demand for heat, the first stage thermostatic switch 149 will be closed as shown in FIG. 10 to energize the first stage heat motor 143 to commence heating of the temperature sensitive rod 135. Heating of the temperature sensitive rod 135 will expand such rod to thereby enable the upper extremity of the vertical link 121 to rotate to the left thus drawing the diagonal link 127 slightly to the left and urging the free extremity of the lever to the left thereby tending to drive the index plunger 113 (FIG. 6) out of the index groove 103. When the temperature sensitive rod has been heated sufficiently to grow adequately to enable sufficient force to be created by the coil spring 133 to urge the cam shaft 31 to the left with sufficient force to drive the index plunger 113 out of the index groove 103, such cam shaft will be urged abruptly to the left thus shifting the blower control cam 33 abruptly to the left and out of alignment with the free extremity of the blower control blade 71 thus freeing the electrical contact 75 to snap rapidly against the electrical contact 79 as shown in FIG. 3 to rapidly make electrical contact to minimize arcing between such contacts.

As heating of the temperature responsive rod 135 continues, such rod will continue to grow in length thus resulting in the coil spring 133 continuing to urge the cam shaft 31 to the left with greater force until the index plunger 1 13 is raised out of the index groove 105 to enable such shaft to be again shifted abruptly to the left thus shifting the cam 35 clear of the free extremities of the blades 23 and 25 (FIG. 5) carrying the

contacts

27 and 29 controlling current to the first electrical heating element. As such shaft 31 is shifted abruptly to the left, the free extremity of the

blades

27 and 29 will ride inwardly along opposite sides of the symmetrical frustum surface 95 thus carrying the

contacts

27 and 29 inwardly toward one another at equal and opposite speeds thus causing such contacts to engage one another with a minimum amount of rebound force and minimizing bounce and consequent electrical arcing between such contacts which may resuit in liquifying a portion of the surface contact metal and consequent welding together of the contacts.

As the temperature sensitive rod 135 grows further, the cam shaft 31 will be shifted further to the left thus engaging the index plunger 133 in the index groove 107 and shifting the cam 37 clear of the free extremities of its associated

blades

23 and 25 to enable the

contacts

27 and 29 carried thereby to make electrical contact with one another to energize the second heating element of the furnace.

If the temperature sensed by the thermostat continues to fall, the second stage thermostat switch 151 will be closed as shown in FIG. 9 to energize the second stage heat motor 145 to induce further heating and growth of the temperature sensitive rod 135. Such further heating and growth of the rod 135 will shift the cam shaft 31 further to the left thus shifting the cam 39 clear of the free ends of the associated

blades

23 and 25 and subsequently shifting the cam 41 clear of the free extremities of the associated

blades

23 and 25 thus energizing the last two furnace heating elements in sequence.

As the temperature sensed by the thermostat is raised, the second stage thermostat switch 151 will be opened to de-energize the second stage heat motor 145 to commence cooling of the temperature sensitive rod 135 and consequent shrinkage of such rod to tend to draw the upper extremity of the lever 115 (FIG. 9) to the right thus raising the index plunger 113 out of the index groove 111 and enabling the shaft 31 to shift to the right thus engaging the frustrum surface 101 with the free extremities of the associated

blades

23 and 25. The frustrum surface 101 will wedge between the

blades

23 and 25 to separate such blades to break electrical contact between the

contacts

27 and 29 to open the circuit to the fourth furnace heating element. In practice, the frustrum is forced against the

blades

23 and 25 with sufiicient force to create a contact breaking force of approximately one pound thus assuring breaking of any weld that may have developed between the

contacts

27 and 29. Likewise, the frustrum 99 of the cam 39 will subsequently be wedged between the free extremities of the associated

blades

23 and 25 to separate the

contacts

27 and 29 completing the circuit through the third furnace heating element.

Thereafter, if the temperature sensed by the thermostat continues to rise, the first stage thermostat switch 149 will be opened to de-energize the first stage heat motor 143 and permit further cooling of the tempera ture sensitive rod 135 to sequentially effect breaking of the circuit between the remaining

contacts

27 and 29 controlling current to the second and first heating elements of the furnace. it will be appreciated that the switch 57 controlling current to the blower is the last to open thus continuing blowing of air over the heating elements to prevent overheating thereof and provide for forced air circulation.

If it is desirable to operate the furnace blower at high speeds, the selector switch 84 (FIG. 7) may be closed to energize the solenoid 83 to draw the plunger 85 (FIG. 2) in to flex the common blade 77 to bring the contact 81 into engagement with the contact 76 thus completing a circuit through the high speed circuit of the blower motor. The blower may be actuated in this fashion with or without actuation of the furnace heating elements.

It has been determined that with the cam actuated multiple contact switching device of the present invention each contact pair may carry up to 40 amperes with exceptionally long life. Laboratory tests have shown that the contacts will carry 40 amperes for well over 150,000 cycles without contact welding or serious damage. It will be appreciated that the contacts themselves may be utilized with a cam shaft arrangement that provides for simultaneous opening thereof and such contacts may be employed to cooperate in forming a switching means for a single high current load.

From the foregoing, it will be apparent that the cam actuated multiple contact switching device of the present invention provides an economical and highly reliable means for actuating a plurality of switches while minimizing any tendency of the contacts to weld together and providing a high contact breaking force.

What is claimed is:

1. A cam actuated multiple contact switching device comprising:

a housing;

a plurality of pairs of movable contacts spaced at predetermined spacings;

a plurality of pairs of opposed resilient mounting means mounting said pairs of contacts from said housing, the resilient mounting means of each pair having substantially identical biasing characteristics for movement of the contacts of each pair at equal rates from their respective break positions to their respective make positions;

camming means including a plurality of individual cams coupled together and including identical cam surfaces for engaging the opposed mounting means of said pairs of mounting means and shiftable to enable said mounting means to move said respective pairs of contacts from their respective break positions to their respective make positions at substantially identical rates of speed; and

drive means for driving said cams from their contact make to their contact break positions; and

stepping means coupled with said cams and operative to store energy upon actuation of said drive means and to then release a portion of the stored energy to provide for rapid shifting of said cam means and consequent rapid shifting of said contacts between their make and break positions.

2. Cam actuated multiple contact switching device as set forth in claim 1 that includes:

shaft means carrying said cams in staggered relationship with respect to said predetermined relationship and axially shiftable in one direction to sequentially close said pairs of contacts;

indexing means including an index plunger and biasing means urging said plunger toward said shaft means and indentations spaced along said shaft means for receipt of said plunger to restrict axial shifting of said shaft means with a predetermined force at points immediately prior to said respective cams effecting closure of said respective pairs of contacts and responsive to development of said predetermined force on said shaft means to release said shaft for axial shifting thereof to free said pairs of contacts for rapid positive closing thereof.

3. Cam actuated multiple contact switching device as set forth in claim 1 wherein:

said drive means includes a lever carried pivotally on one end from said housing and engaging said camming means on its free extremity, a first link pivotally connected on one end with said housing projecting coextensive with said lever and a diagonal link pivotally connected on one end with the free a plurality of pairs of resilient mounting means mounting said pairs of contacts from said housing for movement of the contacts of each pair from their break positions to their make positions;

extremity of said first link and on its opposite end camming means including a plurality of individual with the lever adjacent said one end thereof and a cams coupled together and arranged in staggered thermally expansive element connected with said relationship with respect to said mounting means first link adjacent said one end thereof and a heat for sequential engagement therewith upon shifting motor disposed in heat exchange relationship with of said camming means to move said respective said thermally expansive element for heating 10 pairs of contacts from their respective make posithereof to rotate said first link and said lever to shift said shaft means.

tions to their respective break positions; stepping means operative to engage said camming 4. Cam actuated multiple contact switching device as set forth in claim 1 that includes:

an auxiliary switch including a common contact inmeans prior to making of each said pair of contacts to resist shifting of said camming means and to store energy and to then release a portion of the terposed between a selected pair of said pairs of contacts and selector means coupled with said common contact and including electromagnetic means for selectively engaging said common contact with one or the other of said contacts of said selected pair.

stored energy to provide for rapid shifting of said cam means and consequent rapid shifting of said contacts between their make and break positions; and

drive means for driving said cams from their contact break to their contact make positions whereby said 5. A cam actuated multiple contact switching device drive means may be actuated to urge said cams comprising: toward their make positions and said stepping a housing; means will cause periodic release to cause stepa plurality of pairs of movable contacts spaced at premaking of said pairs of contacts. determined spacings;

Claims

1. A cam actuated multiple contact switching device comprising: a housing; a plurality of pairs of movable contacts spaced at predetermined spacings; a plurality of pairs of opposed resilient mounting means mounting said pairs of contacts from said housing, the resilient mounting means of each pair having substantially identical biasing characteristics for movement of the contacts of each pair at equal rates from their respective break positions to their respective make positions; camming means including a plurality of individual cams coupled together and including identical cam surfaces for engaging the opposed mounting means of said pairs of mounting means and shiftable to enable said mounting means to move said respective pairs of contacts from their respective break positions to their respective make positions at substantially identical rates of speed; and drive means for driving said cams from their contact make to their contact break positions; and stepping means coupled with said cams and operative to store energy upon actuation of said drive means and to then release a portion of the stored energy to provide for rapid shifting of said cam means and consequent rapid shifting of said contacts between their make and break positions.

2. Cam actuated multiple contact switching device as set forth in claim 1 that includes: shaft means carrying said cams in staggered relationship with respect to said predetermined relationship and axially shiftable in one direction to sequentially close said pairs of contacts; indexing means including an index plunger and biasing means urging said plunger toward said shaft means and indentations spaced along said shaft means for receipt of said plunger to restrict axial shifting of said shaft means with a predetermined force at points immediately prior to said respective cams effecting closure of said respective pairs of contacts and responsive to development of said predetermined force on said shaft means to release said shaft for axial shifting thereof to free said pairs of contacts for rapid positive closing thereof.

3. Cam actuated multiple contact switching device as set forth in claim 1 wherein: said drive means includes a lever carried pivotally on one end from said housing and engaging said camming means on its free extremity, a first link pivotally connected on one end with said housing projecting coextensive with said lever and a diagonal link pivotally connected on one end with the free extremity of said first link and on its opposite end with the lever adjacent said one end thereof and a thermally expansive element connected with said first link adjacent said one end thereof and a heat motor disposed in heat exchange relationship with said thermally expansive element for heating thereof to rotate said first link and said lever to shift said shaft means.

4. Cam actuated multiple contact switching device as set forth in claim 1 that includes: an auxiliary switch including a common contact interposed between a selected pair of said pairs of contacts and selector means coupled with said common contact and including electromagnetic means for selectively engaging said common contact with one or the other of said contacts of said selected pair.

5. A cam actuated multiple contact switching device comprising: a housing; a plurality of pairs of movable contacts spaced at predetermined spacings; a plurality of pairs of resilient mounting means mounting said pairs of contacts from said housing for movement of the contacts of each pair from their break positions to their make positions; camming means including a plurality of individual cams coupled together and arranged in staggered relationship with respect to said mounting means for sequential engagement therewith upon shifting of said camming means to move said respective pairs of contacts from their respective make positions to their respective break positions; stepping means operative to engage said camming means prior to making of each said pair of contacts to resist shifting of said camming means and to store energy and to then release a portion of the stored energy to provide for rapid shifting of said cam means and consequent rapid shifting of said contacts between their make and break positions; and drive means for driving said cams from their contact break to their contact make positions whereby said drive means may be actuated to urge said cams toward their make positions and said stepping means will cause periodic release to cause step-making of said pairs of contacts.