INTEGRAL CAM OPERATED ROTARY SWITCHES

FIELD OF INVENTION

The present invention relates o the rotary switches, in particular to integral cam operated rotary switches wherein the circuits are activated in one or more switch positions (settings) and wherein a programmed activation of said load circuits are provided. Specifically, the present invention provides for rotary switches which are adaptable for use as both NO (normally open) and NC (normally closed) switches. Advantageously, the present invention relates to a compact and cost effective integral cam operated rotary switch which can be assembled easily, thereby reducing the assembly time. Moreover, the number of contacts used are reduced to optimum level so that the overall size and weight are reduced thereby making the wiring simple.

BACKGROUND OF ART

A switch is an electro mechanical component, which control a circuit in its simplest form. A switch has two operational positions in one of which a circuit is made (or closed) and in the other it is broken (or opened). A switch is therefore, said to be 'open' or 'closed' depending on which operational position it is in. Most circuits require a switch to be open in the normal course and closed when desired. Such switches are called NO or 'normally open' switches. Similarly, there are 'normally closed' or NC switches. The rotary switches of this invention area adoptable for use as both NO and NC switches.

A simple circuit comprises a source of electrical energy and a load and conductors extending from source of load and back such as to complete a circuit round which a current could flow. The load may be any device or component that uses electrical energy. The source may be a single phase or three phase supply with or without neutral. In certain cases it may be an output of a current transformer or voltage transformer. The switch is interposed in a circuit either on the conductor outgoing from the source or on the conductor incoming to the source or on the both.

As mentioned herein above, a simple switch has a pole and a load terminal. It further has contact(s) made out of metallic contacts which upon closing of the switch provide continuity for the current flow from pole to load terminal. A contact comprises a pair of contact elements (surface) which upon operation of the switch establish electrical contact with each other. A double contact comprises two pairs of contact elements (surface) which, the switch is operated come simultaneous into electrical contact with each other. Double contacts in switches can be in series or in parallel, the former being more common in double butt contacts. This point is further elaborated herein below.

A contact, as mentioned, comprises two contact elements (surface) which establish electrical contacts such as to close a circuit, commonly one of the contact elements is stationary which the other moves towards it establish contact of the surface. The movement of the moving element may be sideways with respect to the contact surface or frontal. In case of the former, two contact surfaces slide over each other before coming to restfully abutting each other. Such contacts are called wiping contacts because of certain amount of mutual wiping of the contact surfaces take place during said movement. In the case of the later, the moving contact surface moves frontally till it comes to rest abutting the stationary contact surface. In this case, no wiping action occurs. This type of contact is called a butt contact. Both double wiping type and double butt type contacts are found in the art.

A simple rotary switch comprises pole and a set of load terminals wherein contact between pole and load terminals is provided by a moving member which is in contact with the pole and which, as it moves, successively makes contact with the load terminals. Modern rotary switches are, however, more complex and standardized. The selective switching action between pole(s) and load terminal(s) in a rotary switch is now carried out in a unit, which is called a switching module. Switching modules are standardized and a rotary switch may comprise one or more of switching modules. Switching modules are also referred to in the art as decks, packets and stages and by other terms.

A switching module essentially comprises a shaft, the rotation whereof causes selective switching action to take place in the module. At one end of shaft is mounted selection means such as knob or handle or others by means of which shaft is rotated and placed into various angular positions corresponding to settings of the rotary switch. Detent means provide firm location of the shaft in its various angular positions. Adjacent selector means a faceplate is located on the shaft. The shaft has markings thereon indicating the settings of the switch and also pictorial and/or written information about settings, the load(s) energized in each setting and other information.

The shaft is mounted on the faceplate and the faceplate is provided with screw means or other fixing means for mounting upon a switchboard or control panel. Thus the rotary switch, in this case is mounted on a panel, Switchboard through the means of the faceplate. In other cases, particularly where the rotary switch to be mounted is somewhat bulky shaft is provided with means to mount it on panel/switch board.

In yet other cases, the mounting means are provided on the body of the rotary switch for mounting the same on panel/switchboard. In the last two mentioned types of mounting arrangements the faceplate becomes redundant and the information thereon is provided on the panel/switchboard itself.

As regards mounting of rotary switches, front mounting, rear mounting and split mountings are practiced. The difference between these is marginal and the switches of the invention are equally adaptable to all these application. Optionally, there is a faceplate, which sometimes also serves the function of said mounting means. Generally speaking, rotary switches adapted for multi circuit operation have a plurality of switching modules. In fact, the number of switching modules required depends upon either the total number of loads to be energized or the maximum number of loads to be simultaneously energized depending on the type of switching modules to be used.

Switching modules are of two types:

a. Rotary arm type; and
b. Cam type

Rotary switches are also referred to as rotary arm type or cam type depending on the type of switching modules incorporated in them. In rotary arm type switching modules, said selective switching action is performed by an arm which is mounted on said shaft and rotated therewith. In an integral cam type switching modules, said switching action is done by means of cam wheel(s)/disc(s) mounted on said shaft and rotatable therein. With regard to rotary arm type rotary switches it will be observed that if a particular load forms part of, say, three load combinations then, that load will have three load terminals one each in each of the three load terminal arrays associated with these combinations. It is necessary then to interconnect these three load terminals with the help of specially designed jumpers. A jumper is a substantially rigid metallic component such as of pressed copper strip or copper wire fixable between two or more load terminals to provide interconnection there between. Consider a typical application where a rotary switch supplies power to a set load terminals in a programmed manner. This applies to both rotary arm type and cam type rotary switches. If a load, appears in three load combinations then in case of the rotary arm type units they would have to be interconnected by jumpers. In contrast, in a cam type rotary switch only one load terminal is associated with each load and so the necessity for interconnecting load terminals with jumpers does not at all arise in cam type units.

There has been a long term trend for higher degrees of miniaturization of electronic components. Consistent with that trend, components such as rotary switches have been substantially reduced in size, and further size reductions are still demanded. The structure of the prior art rotary switches, makes such ultra-miniaturization difficult to achieve while maintaining performance criteria, such as accuracy and reliability. In the existing rotary switches a large number of unwanted contacts are available which increases the possibility of wrong connections of wires. Moreover, none of the existing cam operated rotary switches can be readily adopted both as a normally opened as well as normally closed switches.
Therefore, it is desirable to provide a cam type rotary switch with simplified construction and which can be easily adopted to normally open as well as normally closed switches.

OBJECTS OF THE INVENTION

It is the primary object of the present invention to provide an integrated cam operated switch for programmed operations.

It is another object of the present invention to provide an integrated cam operated rotary switch which is compact, lighter and more economical.

It is another object of the present invention to provide an integrated cam operated rotary switch which can be used for inductive loads unlike the rotary arm type units.

It is another object of the present invention to provide an integrated cam operated rotary switch, wherein the double butt contacts offer far smoother operation of the switch involving less effort.

It is another object of the present invention to provide an integrated cam operated rotary switch with a unique design of hosing, top cover and bottom cover which can be assembled easily and assembly time also reduced.

It is another object of the present invention to provide an integrated cam operated rotary switch with reduced size thereby saving plastic component, weight and number of contacts.

It is another object of the present invention to provide an integrated cam operated switch which is compact and cost effective.

It is another object of the present invention wherein the terminal numbers are permanently marked thereby the wiring is made easy and can't be missed out.

It is another object of the present invention which reduces the availability of unwanted contacts thereby ensuring fool-proof wiring.

It is another object of the present invention, wherein a single housing with top and bottom covers is provided.

It is another object of the present invention, wherein the top and bottom covers are designed with locks, which can be fastened to the housing without screws.

SUMMARY OF INVENTION

Thus according to the basic aspect of the present invention there is provided an integral cam operated rotary switch having plurality of switching positions and switching angles in which the detent function is integral with the contact operating cam function comprising:
housing;
shaft;
detent; and
one or more contacts,

wherein said detent comprises a cam wheel mounted on the shaft and a spring means to provide firm location of the shaft in the determined angular positions, wherein said contact(S) is selected from a combination of fixed contact and movable contact,

wherein said moving contact is located in a contact slide which acts as a follower for the cam wheel and the contact slide is loaded by contact spring, and wherein said contact(S) being activated by cam wheels upon rotation thereof such as to provide programmed interconnections between sets of poles and load terminals.

In the above said invention, said shaft is provided with a handle, knob or the like means for rotation into various angular positions corresponding to the settings.

Also in the said invention, the said contacts are spring loaded double butt contacts.

It is another aspect of the present invention, wherein the cam profile is designed in accordance to the torque and detent functions.

According to another aspect, the cam is provided with stopping arrangement integrated with the body of the switch.

According to yet another aspect, the integral cam operated rotary switch further comprising switching module, wherein said switching module is provided with the housing whose assembly comprising:

top cover;
bottom cover;
terminal screws;
terminal clamp;
mounting plate;
front plate;
script plate; and
raster plate,

wherein said top and bottom covers are designed with locks to fix firmly to the housing without screws,

wherein said terminal screws and terminal clamp are used for tightening the incoming and outgoing wires in the circuit,

wherein said mounting plate is an integral part of the housing for fixing the switch in the panel/switchboard,

wherein said front plate is used for fixing the script plate,

wherein said script plate assembly is fixed to the panel/switchboard in the mounting plate, and
wherein said raster plate provided in the switch is sandwiched between the panel/switchboard and the mounting plate.

It is another aspect of the present invention, wherein the switch contact is fastened together by snap fit or fasteners with the cams, contacts, followers, springs and providers for termination of incoming and outgoing conductors in which the common poles are integral with single termination.

It is another aspect of the present invention, wherein a panel mounting arrangement with or without switching positions marked on the same is provided.

It is another aspect of the present invention, wherein as the switch operating mechanism is rotated, the cam wheels rotates thereby pushing the spring-loaded followers away from the axis of the switch which thereby stores the energy for half of the rotation of the switching angle, wherein as the operating mechanism is rotated beyond half of the switching angle, the spring releases the energy thereby pushing
the cam and the switch shaft to the next position, wherein the arrangement is made for each of the switching contact, which shall be switched in their respective switching angles and wherein the orientation between the cam portion on the central shaft depends on the switching sequence requirement.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1: illustrates the cross sectional view of the assembled switch of the present invention at the panel mounting side.

Figure 2: illustrates the sectional view of the switch according to the present invention.

Figure 3: illustrates the front latching part assembly according to the present invention.

Figure 4: illustrates the partial exploded view of the switch according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING
DRAWINGS

As mentioned herein above, this invention has developed integral cam operated rotary switch for various advantage. In view of the overwhelming design, operational and economic advantages in favor of cam type rotary switches this invention has carried further the development of the cam type rotary switch to the stage of full fledged commercial prototype incorporating other features known in the art and desired by the users. In addition, cam type units have overwhelming operational advantage over the rotary arm type units that includes cam type rotary switches can be used for inductive loads unlike the rotary arm type units and the double butt contacts of cam type units offer far smoother operation of the switch involving less effort.

There are flexibilities in the design of cam operated rotary switches such as: Selector Means: This selector means may be a handle or knob several designs of which are known in the art. Some of the designs provide facility for locking knob or handle.

Face Plate: This component indicates the positions of the various settings and may further have information, pictorial or otherwise of the load energized at different settings. The information provided on the faceplate is sometimes indicated on the control panel/switchboard on which the rotary switch is mounted. In that case the faceplate can be dispensed with.

In the embodiment described in detail herein below, the faceplate also performs the function of mounting. The rotary switch is mounted on the face plate which, in turn, is mounted upon a panel/switchboard by means of screw/snap hooks is designed to fit various standardized switchboards marketed by various companies. The face plate has been given suitable treatment to provide good visibility and is provided with an LED which indicates whether the power is ON.

Mountings: For medium and large sized rotary switches it is rather not feasible to mount them on faceplates. Medium sized units often have screws provided on the shaft of the selector and the detent assembly such that the shaft and the switch is mounted in a suitable sized hole provided in the control panel or switchboard. Larger sized units are province with brackets, and if necessary be rods, for mountings directly onto the panels/switchboards. Mounting arrangements are varied. Some units are mounted on the front panel/board of the control panel/switchboard and others on the rear panel/board thereof. Some units have split mounting that is, part of the unit is mounted at front and part at the rear.

Detent: The switches of the invention may incorporate any of the different design of the detent available in the art. A typical detent comprises a substantially cylindrical box the inside circular surface of which is contoured to correspond with the switch settings, that is, having valleys and ridges at corresponding angular distances. An elongated member having cam like ends rotates with the switch shaft the cam like ends being spring loaded. As the cam like ends follow said contours they move to and fro radially causing the spring to alternatively absorb and release energy. During the phase in which the springs release energy they urge the elongated member and the switch shaft to move precisely into the adjacent setting position. Instead of the elongated member in the embodiment described in detail herein below, there is a cam wheel having several cams like ends located on the circumference thereof. The detent also have stop for stopping the rotation of the shaft at a desired point. This is useful where the settings of the switch do not extend the full 360 degrees of a circle and it is necessary to put a limiting stop to the movement of the selector.

Shaft: The shaft may comprise of a single shaft extending from the selector knob to the last of the switching modules. Alternatively, in accordance with this invention the shaft may comprise segmental shaft one for the knob and detent assembly and one each of for each of the switching modules. Single shafts of rotary switches are often of metal particularly if the switch has a large number of modules. However, as segmental shafts are of smaller lengths plastics can be conveniently used.

Settings: In the embodiment described in detail, the rotary switch has been provided with different angular settings. The lowest practical value of angle in the art is considered to be 15 degree giving a maximum of 24 settings including the OFF position.

Reference is now invited to the accompanying Figure 1which illustrates the cross sectional view of the assembled switch of the invention.

The housing (1) of the switching module and the top (2) and bottom cover (3) which covers the housing are fastened together. The camshaft (4) is located and housed in the housing for enabling the contacts to open and close the circuit along with the detent assembly in latching part (11). The fixed contact (5) is a stationary metallic component which is riveted by a silver cladded button which is located in the housing on both the sides of the housing for making and breaking the circuit when the moving contact moves to and fro with respect to the cam shaft's profile which are pre determined for the switching sequence. The moving contact (6) is located in the contact slide (7) which acts as a follower for the cam wheel and the contact slide is loaded by the contact spring (8) to have sufficient force for opening and closing the contacts and for detent function which happens simultaneously. The terminal screws (9) and terminal clamp (10) are used for tightening the incoming and outgoing wires in the circuit.

The housing (1) is designed in such a way that it makes the cam and contact assembly easier so that the assembly time can be reduced to a considerable amount. The top and bottom covers are designed with locks so that these can be fastened to the housing without screws. The front latching plate (11) as depicted in Figure 2 is an individual part which serves as a housing for latching assembly and mounting plate (16) for fixing the switch in the panel /switchboard. The detent portion of the cam wheel is made in such a way it stores and releases the energy keeping the contact in open position. The curvature is developed for the required torque of operating the switch. The curvature is different for the detent function. As the switch operating mechanism is rotated, the cam wheels rotate thereby pushing the spring-loaded followers away from the axis of the switch. This stores the energy for half of the rotation of the switching angle. The switching angle is defined as the angle between the two adjacent detent positions. As the switch operating mechanism is rotated beyond half of the switching angle, the spring releases the energy thereby pushing the cam and the switch shaft to the next detent position. This arrangement is made for each of the switching contact which shall be switched in their respective switching angles. The various earns, equal in number to the number of contacts are integral made of single material. The orientation between the cam portions on the central shaft depends on the switching sequence requirement. Depending on the requirement this integral cam may have a stopping arrangement with the body of the switch.

The mounting plate (16) is an integral part of the housing for fixing the switch in the panel/ switchboard. Referring to Figures 2, 3 and 4, the front plate (15) is used for fixing the script plate (19) and the script plate assembly is fixed to the panel/switchboard by means of the mounting plate fixing screw (12) in the mounting plate (16). The switch is operated by the knob/handle (14) which is tightened by means of knob screw (17) to the knob shaft (13). A raster plate (18) provided in the switch which is sandwiched between the panel/switchboard and the mounting plate.

WE CLAIM:

1. An integral cam operated rotary switch having plurality of switching positions and switching angles in which the detent function is integral with the contact operating cam function comprising:

housing (1); shaft (4); detent; and
one or more contacts (5,6),

wherein said detent comprises a cam wheel mounted on the shaft (4) and a spring means to provide firm location of the shaft in the determined angular positions, wherein said contact is selected from a combination of fixed contact (5) and movable contact (6),

wherein said moving contact is located in a contact slide (7) which acts as a follower for the cam wheel and the contact slide is loaded by contact spring (8), and wherein said contact(s) being activated by cam wheels upon rotation thereof such as to provide programmed interconnections between sets of poles and load terminals.

2. An integral cam operated rotary switch as claimed in claim 1, wherein said shaft is provided with a handle, knob or the like means (14) for rotation into various angular positions corresponding to the settings.

3. An integral cam operated rotary switch as claimed in claim 1, wherein said contacts are spring loaded double butt contacts.

4. An integral cam operated rotary switch as claimed in anyone of claims 1 to 3, wherein the cam profile is designed in accordance to the torque and detent functions.

5. An integral cam operated rotary switch as claimed in anyone of claims 1 to 4, wherein the cam is provided with stopping arrangement integrated with the body of the switch.

6. An integral cam operated rotary switch as claimed in anyone of claims 1 to 5, wherein the rotary switch further comprising switching module, wherein said switching module is provided with the housing whose assembly comprising:

top cover (2); bottom cover (3); terminal screws (9); terminal clamp (10); mounting plate (16); front plate (15); script plate (19); and raster plate (18),

wherein said top cover (2) and bottom cover (3) are designed with locks to fix firmly to the housing without screws,

wherein said terminal screws (9) and terminal clamp (10) are used for tightening the incoming and outgoing wires in the circuit,

wherein said mounting plate (16) is an integral part of the housing for fixing the switch in the panel/ switchboard,

wherein said front plate (15) is used for fixing the script plate (19),

wherein said script plate assembly is fixed to the panel/switchboard in the mounting plate, and

wherein said raster plate (18) provided in the switch is sandwiched between the panel/switchboard and the mounting plate.

7. An integral cam operated rotary switch as claimed in anyone of claims 1 to 6, wherein the switch contact is fastened together by snap fit or fasteners with the cams, contacts, followers, springs and providers for termination of incoming and outgoing conductors in which the common poles are integral with single termination.

8. An integral cam operated rotary switch as claimed in anyone of claims 1 to 7, wherein a panel mounting arrangement with or without switching positions marked on the same is provided.

9. A mechanism of operating the switch as claimed in anyone of claims 1 to 8, wherein as the switch operating mechanism is rotated, the cam wheels rotates thereby pushing the spring-loaded followers away from the axis of the switch which thereby stores the energy for half of the rotation of the switching angle, wherein as the operating mechanism is rotated beyond half of the switching angle, the spring
releases the energy thereby pushing the cam and the switch shaft to the next position, wherein the arrangement is made for each of the switching contact, which shall be switched in their respective switching angles and wherein the orientation between the cam portion on the central shaft depends on the switching sequence requirement.