US3719785A

US3719785A - Thumbwheel switch assembly with improved gang housing interlocking means

Info

Publication number: US3719785A
Application number: US00133633A
Authority: US
Inventors: T Kendall; T Lincoln
Original assignee: Becton Dickinson and Co
Current assignee: XCEL Corp; Becton Dickinson Electronics Co
Priority date: 1971-04-13
Filing date: 1971-04-13
Publication date: 1973-03-06
Anticipated expiration: 1990-03-06

Abstract

A case of a switch structure is provided which has a partition wall which extends from the front to the rear thereof and which divides the case into parts. Rotary electrical contacts are mounted on one side of the partition wall and fixed electrical contacts are mounted on a printed circuit board adjacent to the rotary electrical contacts. A cover plate is provided which holds the printed circuit board in place in the switch case against the partition wall. The cover plate has pins formed on the inside thereof which project through corresponding holes formed in the partition wall. The pins also engage notches and a central aperture formed in the printed circuit plate. The pins of the cover plate accurately align the printed circuit plate for cooperation with the rotary electrical contacts. The cover plate is permanently mounted in position by heat staking the ends of the cover plate pins from the opposite side of the partition wall or by means of hooks on the ends of the pins. The cover plate and the printed circuit plate are thus accurately aligned and permanently held in position against the partition wall.

Description

United States Patent [1 1 Kendall et a1.

[54] THUMBWHEEL SWITCH ASSEMBLY WITH IMPROVED GANG HOUSING INTERLOCKING MEANS [75] Inventors: Thomas L. Kendall, Duarte; Thomas C. Lincoln, Arcadia, both of Calif.

[73] Assignee: Bectron, Dickinson Electronics Company, Pasadena, Calif.

[22] Filed: April 13, 1971 [21] Appl.N0.: 133,633

12/1966 Meyer ..200/l68 K X 3/1970 Long 3/1970 Cherry et a1 FOREIGN PATENTS OR APPLICATIONS 5/1970 France ..200/1 1 TW 1 March 6, 1973 Primary Examiner-J. R. Scott Attorney-Reed C. Lawlor [5 7 ABSTRACT A case of a switch structure is provided which has a partition wall which extends from the front to the rear thereof and which divides the case into parts. Rotary electrical contacts are mounted on one side of the partition wall and fixed electrical contacts are mounted on a printed circuit board adjacent to the rotary electrical contacts. A cover plate is provided which holds the printed circuit board in place in the switch case against the partition wall. The cover plate has pins formed on the inside thereof which project through corresponding holes formed in the partition wall. The pins also engage notches and a central aperture formed in the printed circuit plate. The pins of the cover plate accurately align the printed circuit plate for cooperation with the rotary electrical contacts. The cover plate is permanently mounted in position by heat staking the ends of the cover plate pins from the opposite side of the partition wall or by means of hooks on the ends of the pins. The cover plate and the printed circuit plate are thus accurately aligned and permanently held in position against the partition wall.

7 Claims, 7 Drawing Figures PATENT EDHAR 61975 }-SHEET10F 2 77/0/1445 A. KE/Vfiflll 77/0/1445 C. A//VCOL/V INVENTORS Ill l'lllllulllllql 1 THUMBWHEEL SWITCH ASSEMBLY WITH IMPROVED GANG HOUSING INTERLOCKING MEANS CROSS REFERENCES TO RELATED APPLICATIONS U.S. Pat. application Ser. No. 133,602, filed Apr. 13, 1971 now Pat. No. 3,655,925.

SUMMARY OF THE INVENTION This invention provides a switch structure having a case with wall members. First electrical contacts formed on an electrical contact carrying member are mounted in the switch case. Second electrical contacts are mounted in the case in order to cooperate with the first contacts for making and breaking circuits. Plate means are mounted adjacent to said wall members to hold said contact carrying member in position. In-

terengaging means are formed in said wall members and in said plate means in order to hold said plate means and said contact carrying member in position on said switch case.

BRIEF DESCRIPTION OF THE DRAWINGS The presently preferred form of the invention is disclosed in the accompanying drawings wherein:

FIG. 1 is a perspective view of an assembly of switch structures embodying the invention;

FIG. 2 is a perspective exploded view of a switch structure of one embodiment of the invention;

FIG. 3 is a plan cross sectional view taken along the DESCRIPTION OF THE FIRST EMBODIMENT FIGS. 1 and 2 show an assembly of switch structures of this invention mounted on a switch panel 11. Each switch structure includes a switch unit 10 which may be assembled in line with other switch units to form a switch structure assembly as is shown in FIG. 1. The ends of the assembly are then closed with end plates or end brackets 12. The end plates 12 are secured to switch panel 11 by screws 13 or the like. A single switch, comprising a switch unit 10 and two end plates 12, may also be mounted on a switch panel 11. Although this invention may be employed in many different types of switch structures, only one type of switch structure will be described herein.

FIG. 2 shows the relationship of the several parts of the switch unit 10 of the switching structure of this invention. The switch unit 10 comprises a case or housing 20 which is preferably cast or molded from an electrical insulating material, such as any appropriate wellknown thermoplastic resin. As may be seen in FIGS. 2-5, the case or casing 20 is molded with a top wall 22, a bottom wall 23, a back wall 24, and a front wall 25. Angular end brackets or end plates 12 close the two sides of the switch structure and form side walls for the switch unit case 20. The front flanges of end plates 12 provide means for mounting the switching structure on a switch panel or the like, as has been previously described. Interengaging members, such as pins 14 and complementary holes 15 are provided at the corners of the case 20 and in the angular end brackets 12 so that the end brackets 12 are securely and accurately positioned on the sides of the case 20. Other similarly constructed switch units 10 may also be assembled side-byside with the aid of pins 14 and holes 15 as is shown in FIG. 1. The end brackets 12 are then mounted on the two ends of the entire switch assembly.

As is shown in FIGS. 1-4, recess 16, formed in top wall 22, bottom wall 23, and end brackets 12, receives securing means 18 in the form of a metal band or the like which holds the parts of the switch structure together. Securing means 18 is more fully discussed in my copending U.S. Pat. application Ser. No. 133,602, filed Apr. 13,1971.

Longitudinal partition wall 30 is integral with the top, bottom, rear and front

exterior case walls

22, 23, 24, and 25 respectively and divides the case into two parts or areas. The partition wall 30 lies entirely between the sides of the case 20. Recessed electrical parts chamber or well 32 is formed in the partition wall 30 and receives the rotary electrical contacts or fingers 56, to be more fully explained hereinafter. Another chamber or space 34 is provided on the other side of the partition wall 30. Cylindrical protrusion 36, corresponding to the well 32, is provided by partition wall 30 in space 34. The cylindrical protrusion 36 has a flat end wall 36a and an annular conical ring-shaped side wall 36b. The protruding portion extends in an axial direction parallel to the front of the casing.

Basin 35, seen in FIGS. 3 and 4, is formed between back wall 24, top wall 22, and bottom wall 23 and the rearward edge of well 32. Basin 35 is adapted to receive wire terminals, well known to those skilled in the art, in place of printed circuit terminals 47 and connectors 48 to be described hereinafter, if a shortened circuit board is desired and projecting wire terminals are employed. Such a circuit board with wire terminals is shown in Lien U.S. Pat. No. 3,306,993.

Each case 20 has an outer cover wall or cover plate 38 which, when installed, is substantially flush with the outer edges of each

wall

22, 23, 24, and 25. Attached to the inside face of the. cover plate 38 are interengaging means or pins 39 which extend into corresponding interengaging means or holes 40 and through the partition wall 30. The interengaging means interlock the cover plate and case walls to prevent relative movement thereof in an axial direction, as well as to prevent relative movement thereof in a direction parallel to the front wall. When the cover plate 38 is mounted in its flush relation, the ends of the pins 39 projecting into the space 34 are riveted by a heating process, called heat staking, as is shown in FIG. 3a, so that the cover plate 38 is maintained fixed in position.

Electrical contact carrying members or circuit board 41, composed of dielectric, or electrical insulation, material, is mounted between cover plate 38 and partition wall 30. Circuit board 41 is aligned and held'in place against lands 43 on partition wall 30 by the cover plate 38 and the cover plate pins 39 which bear against shoulders 42 of the circuit board and one of which extends through central apertures 44 of circuit board 41.

Cover plate 38 also carries pin 390, shown in FIG. 3, which extends through central aperture 44 of circuit board 41. Pin 39a terminates short of brush holder 54 and does not contact the brush holder 54. However, pin 39a provides a mechanical stop which is adapted to maintain brush holder 54 in place if the brush holder moves towards the circuit board 41. Pin 39a is aligned with shaft 58 on the horizontal rotary switch axis X-X. Axis XX forms the rotary axis for the wheel 60, shaft 58, and the brush holder 54 and is parallel with the front wall 25 of the switch case.

As may be seen in FIGS. 2 and 3, cover plate 38 fits snugly against the insides of the front wall 25, the top wall 22, and the bottom wall 23. The cover plates extends rearwardly to the back of the basin 35.

Another method of permanently securing the cover plate in position is by forming hooks 39b, shown in FIG. 4a, or the like on the ends of the pins 39 which, when pushed through the holes 40 in the partition wall 30, hook onto the partition wall 30 in the space 34 and thereby prevent the pins from being withdrawn.

The outside of the cover plate 38 is smooth and flush with the outer edges of the

walls

22, 23, 24, and 25 so that there are no projections to interfere with the operation of the thumbwheel 60 of a switch unit which is assembled next to the cover plate 38, as is shown in FIG. 1.

Cover plate 38, and the pins 39 and 39a, hold and align the circuit board in position for cooperation between the electrical contacts 46 and the rotary contact 56, as will be explained hereinafter. The cover plate 38 holds the circuit board 41 firmly and permanently against the lands 43 when the pins 39, which extend into the space 34, are heat staked. This construction and the mounting of cover plate 38 prevents damage to the electrical parts from dust and larger particles which might otherwise enter into the well 32 and thereby interfere with the electrical functions of the switch.

Thus, a cover plate is provided which accurately locates the circuit board in place and which permanently and firmly holds the circuit board and the cover plate'in position when the pins of the cover plate are heat staked. In addition, the cover plate prevents damage to the electrical parts from dust and the like which might otherwise enter the electrical parts chamber or well 32 of the switch.

Circuit board 41 may be a printed circuit board, or otherwise, as desired. In any event, circuit board 41 carries on its face opposite the partition wall 30 a plurality of mutually insulated segmental arcuate stationary contacts 46, as may be seen in FIG. 3. At the rearward end of circuit board 41, which extends outwardly from rear wall 24, are typically carried appropriate electrical terminals 47, shown in FIG. 5, which are electrically connected to contacts 46 through printed conductive leads 48. Suitable holes 49 are provided at the end of the circuit board through the terminals 47 in order that suitable electrical connections may be made to the terminals 47.

Operating in conjunction with the segmental electrical contacts 46 on the circuit board 41 is a rotary switch plate or brush holder 54. Brush holder 54 carries on its face opposite the contacts 46 a plurality of rotary electrical contacts 56 in the form of resilient metal brushes, or wiper fingers, which are electrically connected together and appropriately mounted by means of a metal segment 57 (see FIG. 4) in a manner known to perform the required switching functions. An annular ridge or rim 33, located inside the well 32, provides an annular track on which the brush holder 54 rides. Rotary brush holder 54 is rigidly mounted on one end of a shaft 58 by which the rotary brush holder 54 is operated. The shaft 58 is rotatably borne in a bore 59 which is integrally molded at the center of the well 32 and wall 36a of cylindrical protrusion 36.

The operation of the rotary brush plate 54 by means of the shaft 58 is effected by an indicia carrying switching wheel or switch wheel 60 that is rotatably mounted in the space 34, as is shown in FIGS. 2, 3, and 5. Wheel 60 is secured to shaft 58 and rides on partition wall 30 around the periphery of the cylindrical protrusion 36. Switch wheel 60 includes a peripheral, radially directed, flange 62 which is arcuately notched at 64 to provide finger lugs 65 to be engaged by an operator's finger for rotation of the wheel 60 by a tangential finger movement. The outer side wall or face of this wheel, when in operative position, is set slightly within the corresponding outer edges of the

walls

22, 23, 24, and 25 of the case 20 so that the wheel 60 may rotate freely when another case 20 or an end bracket 12 is assembled alongside thereof.

The inner side of the wheel 60 is provided with the concentric inwardly directed cylindrical rim or flange 66 which carries various indicia, such as the digits 0 to 9 of the decimal system, or other indicia as may be required. The cylindrical rim 66 encircles the cylindrical protrusion 36; and is located in plane P'P which extends transversely through window 68, protrusion wall 36b, and rim 66; as is shown in FIG. 3. The inward periphery of the cylindrical rim 66 rides on the partition wall 30 around the outside of the cylindrical protrusion 36.

Wheel 60 is thus arranged to present to view a chosen digit or other indicium through a window 68 in the front wall 25 of the case 20, as is best indicated in FIG. 2. Finger lugs 65 protrude through an aperture 70 in the front wall 25 of the case 20 for engagement by the finger of an operator.

The wheel 60 is slidably keyed to one end of drive shaft 58 and the rotating brush holder 54 is fixed on the other end of the drive shaft. The drive of the shaft 58 by the finger lugs 65 of the wheel 60 is effected through a key 74 which is integrally molded on the end of the shaft 58 and which engages the thumbwheel 60. Key 74 is a semicircular projection at the end of the shaft 58 which snugly fits into a corresponding semi-circular opening 76 in the center of the wheel 60. While the rotary brush holder 54 is rigidly fixed to the inner end of the drive shaft 58, the wheel 60 is axially slidably mounted on the key 74. Sufficient pressure to maintain the wheel 60 on the shaft 58 and the brush holder 54 in the well 32 is effected through the medium of the brushes or wiper fingers 56 which are spring-like in nature. The resilient fingers 56 are partially compressed in the well 32 against the printed circuit board 41 and the contacts 46. An end bracket 12 maintains the switch wheel in the space 34.

In order to assure centering of the indicia in the window 68, a bent detent spring 78 is mounted in the rear of the space 34. The spring 78 includes a forwardly extending portion 79 which is fitted under a pin or stop 80, shown in FIG. 5, and the top wall 22 to retain the spring in the operative position illustrated with the heel of spring 78 fitting against the back corner portion 82 of the top wall 22 and back wall 24. For positioning the wheel 60, the lower end of the spring 78 is provided with an angularly offset portion 83 which drops into one of the finger notches 64 and engages two adjacent finger lugs 65, thereby properly centering the appropriate indicium in the window 68.

A stop 86, in the form of a projection, is integrally formed on the exterior of the cylindrical protrusion 36 near the front wall 25 of the case 20. Holes 88 are provided in side wall of the wheel 60 in order that stops or pins 90 projecting through the holes 88 will engage stop 86, thereby selectively limiting the rotation of the wheel 60.

From the foregoing, it will be apparent that a switch structure construction as provided in which the electrical contacts are accurately aligned and held permanently and firmly in place on the switch case. in addition, damage to the electrical parts from dust or from larger particles is avoided.

At the same time, the structure provides a unit which is such that a series of similar such modular switches may be aligned together in an assembly of units and the construction of each unit will not interfere with the operation of adjacent units.

Although only one specific embodiment of the invention has been described herein, it will be obvious that the invention is not limited thereto but is capable of being embodied in many other forms. Various changes, which will suggest themselves to those skilled in the art, may be made in the material, form, details of construction, and arrangement of the parts without departing from the invention. It is therefore to be understood that the invention is applicable to numerous modifications,

' all within the scope of the appended claims.

The invention claimed is: I 1. A switch structure, comprising: a switch case having wall members;

an electrical contact carrying member mounted adjacent to said wall members and carrying first electrical contacts;

second electrical contacts mounted in said case-and adapted to cooperate with said first contacts to make and break circuits;

plate means mounted adjacent to said wall members to hold said contact carrying member in position in said case; and

interlocking means formed in said wall members and in said plate means, said interlocking means comprising projection members formed on said plate means and projection receiving members formed in said adjacent wall members, said interlocking vmembers positioning and aligning said contact carrying member and holding said plate means and said contact carrying member in place on said switch case.

2. A switch structure as defined in claim ll wherein said electrical contact carrying member comprises a printed circuit plate, said plate means being mounted on the outside of said printed circuit plate to hold said printed circuit plate in said case;

said interlocking means comprising pins formed on the inner side of said plate means, said pins projecting through corresponding holes formed in one of said case wall members and engaging the sides of said printed circuit plate in order to align said printed circuit plate and to hold said printed circuit plate and said plate means in said case, said plate means being permanently mounted in position on the case.

3. A switch structure, comprising:

a switch case having wall members, said wall members having projection receiving means;

rotary electrical contact means mounted on said case and adapted to cooperate with said first contacts to make and break circuits; and

plate means mounted adjacent to said wall members to hold said contact carrying member in position, said plate means having projections formed on the inner side thereof, said projections being interlocked with said contact carrying member and said projection receiving means when said plate means and said contact carrying member are mounted on said switch case.

4. A switch structure as defined in claim 3 wherein said switch case has front, top, rear, and bottom wall members and a transverse wall member extending between the aforementioned four wall members, and further comprising:

an end plate mounted on each end of the switch case to close the sides of the switch case;

interengaging members formed in the switch case which are designed to mate with corresponding interengaging members formed in the end plates in order to accurately align the end plates and the switch case and to prevent movement of the end plates and the switch with respect to each other about a horizontal axis parallel to the said front wall;

said plate means being mounted between one of said end plates and said electrical contact carrying member, said plate means having pins formed on the inner-side thereof which project through corresponding holes formed in said transverse wall member and which engage notches and a central aperture formed in said electrical contact carrying member in order to align said electrical carrying member and to hold said electrical contact carrying member and said plate means in said case, said plate means being permanently mounted in position on said case.

5. A switch structure, comprising:

a case having front, top, rear, and bottom wall members and a transverse member extending between the aforementioned four wall members;

said front wall member having an open window section;

a printed circuit plate composed of insulating material mounted on said case, said printed circuit plate having first electrical contacts formed thereon and having apertures formed therein;

a cover plate mounted on the outside of said printed circuit plate to hold said printed circuit plate in said case, said cover plate having pins formed on the inner side thereof which project through corresponding holes formed in said transverse member and which engage said apertures in said printed circuit plate in order to align said printed circuit plate and to hold said printed circuit plate and said cover plate in said case, said cover plate being permanently mounted in position;

rotary electrical contacts mounted in said case facing in position to cooperate with said first contacts on said printed circuit plate to make and break circuits;

a rotatable indicia wheel mounted in said case, said indicia wheel being coupled to said rotary electrical contacts whereby said indicia wheel and said rotary electrical contacts are adapted to rotate together;

said indicia wheel bearing different symbols on its periphery corresponding respectively to different switch positions, a selected one of said symbols being registered in an indicia indicating position where it is visible through said window when the indicia wheel is moved to one of said different switch positions.

6. A switch structure comprising a stationary switch structure and a rotary switch structure, said stationary switch structure comprising:

a case having front, top, rear, and bottom wall members and a transverse wall member extending between the aforementioned four wall members, said five wall members of said case constituting a unitary rigid structure;

an end plate mounted on each end of said switch case to close the sides of said switch case;

interengaging members formed in the switch case which are designed to mate with corresponding interengaging members formed in the 'end plates in order to accurately align the 'end plates and the switch case and to prevent movement of the end plates and the switch case with respect to each other about a horizontal axis parallel to said front wall;

said transverse wall member providing a recessed well on one side thereof and a corresponding cylindrical protrusion on the other side thereof;

said front wall member having an open window section opposite said cylindrical protrusion;

a bore in the center of the well;

a printed circuit plate composed of insulating material mounted opposite said well and having first electrical contacts formed thereon, said printed circuit plate having an aperture formed in the central portion thereof and notches formed on the sides thereof, said printed circuit plate and said first contacts projecting rearwardly from said front wall;

a cover plate mounted between one of said end brackets and said printed circuit plate, said cover plate having pins formed on the inner side thereof which project through corresponding holes formed in said transverse wall member and which engage said notches and said central aperture of said printed circuit plate in order to align said printed circuit plate and to hold said printed circuit plate against said transverse wall member, said cover plate being permanently mounted in position by heat staking said cover plate pins on the opposite side of said transverse wall member;

said rotary switch structure comprising:

a rotatable brush wheel mounted in said well and bearing second electrical contacts facing and engaging the first contacts on said printed circuit plate;

a rotatable indicia wheel encircling said cylindrical protrusion, said indicia wheel being connected to said brush wheel by shaft means extending through said bore whereby said indicia wheel and said brush wheel are adapted to rotate together;

said indicia wheel bearing different symbols on its periphery corresponding respectively to different switch positions, a selected one of said symbols being registered in an indicia indicating position where it is visible through said window when the indicia wheel is moved to one of said different switch positions;

said indicia wheel also bearing a plurality of radially extending finger lugs on its periphery, successive ones of which are spaced apart by an amount sufficient to receive the distal portion of an operators finger, at least one lug of said wheel projecting at any one time radially outward through said open window whereby said lug is accessible from the front of said switch for operation by the finger of the user;

the top and bottom walls of the switch case and the end plates having a recessed portion extending around the outside of the switch structure;

two ridges formed on each end plate in said recessed portion, said ridges being spaced from the end of each end plate and extending the full width of said recessed portion but being narrow compared with the height of said end plates; and

two identical U-shaped bands adapted to lie within said recessed portion and together to embrace the switch structure and to secure the parts of the switch structure together.

7. A switch structure as defined in claim 6 wherein said interengaging members comprise alternating pins and holes formed on the sides of the walls of the case which are designed to mate with corresponding alternating pins and holes formed on the inside of the end plates.

Claims

1. A switch structure, comprising: a switch case having wall members; an electrical contact carrying member mounted adjacent to said wall members and carrying first electrical contacts; second electrical contacts mounted in said case and adapted to cooperate with said first contacts to make and break circuits; plate means mounted adjacent to said wall members to hold said contact carrying member in position in said case; and interlocking means formed in said wall members and in said plate means, said interlocking means comprising projection members formed on said plate means and projection receiving members formed in said adjacent wall members, said interlocking members positioning and aligning said contact carrying member and holding said plate means and said contact carrying member in place on said switch case.

2. A switch structure as defined in claim 1 wherein said electrical contact carrying member comprises a printed circuit plate, said plate means being mounted on the outside of said printed circuit plate to hold said printed circuit plate in said case; said interlocking means comprising pins formed on the inner side of said plate means, said pins projecting through corresponding holes formed in one of said case wall members and engaging the sides of said printed circuit plate in order to align said printed circuit plate and to hold said printed circuit plate and said plate means in said case, said plate means being permanently mounted in position on the case.

3. A switch structure, comprising: a switch case having wall members, said wall members having projection receiving means; an electrical contact carrying member mounted adjacent to said wall members and carrying first electrical contacts; rotary electrical contact means mounted on said case and adapted to cooperate with said first contacts to make and break circuits; and plate means mounted adjacent to said wall members to hold said contact carrying member in position, said plate means having projections formed on the inner side thereof, said projections being interlocked with said contact carrying member and said projection receiving means when said plate means and said contact carrying member are mounted on said switch case.

4. A switch structure as defined in claim 3 wherein said switch case has front, top, rear, and bottom wall members and a transverse wall member extending between the aforementioned four wall members, and further comprising: an end plate mounted on each end of the switch case to close the sides of the switch case; interengaging members formed in the switch case which are designed to mate with corresponding interengaging members formed in the end plates in order to accurately align the end plates and the switch case and to prevent movement of the end plates and the switch with respect to each other about a horizontal axis parallel to the said front wall; said plate means being mounted between one of said end plates and said electrical contact carrying member, said plate means having pins formed on the inner side thereof which project through corresponding holes formed in said transverse wall member and which engage notches and a central aperture formed in said electrical contact carrying member in order to align said electrical carrying member and to hold said electrical contact carrying member and said plate means in said case, said plate means being permanently mounted in position on said case.

5. A switch structure, comprising: a case having front, top, rear, and bottom wall members and a transverse member extending between the aforementioned four wall members; said front wall member having an open window section; a printed circuit plate composed of insulating material mounted on said case, said printed circuit plate having first electrical contacts formed thereon and having apertures formed therein; a cover plate mounted on the outside of said printed circuit plate to hold said printed circuit plate in said case, said cover plate having pins formed on the inner side thereof which project through corresponding holes formed in said transverse member and which engage said apertures in said printed circuit plate in order to align said printed circuit plate and to hold said printed circuit plate and said cover plate in said case, said cover plate being permanently mounted in position; rotary electrical contacts mounted in said case facing in position to cooperate with said first contacts on said printed circuit plate to make and break circuits; a rotatable indicia wheel mounted in said case, said indicia wheel being coupled to said rotary electrical contacts whereby said indicia wheel and said rotary electrical contacts are adapted to rotate together; said indicia wheel bearing different symbols on its periphery corresponding respectively to different switch positions, a selected one of said symbols being registered in an indicia indicating position where it is visible through said window when the indicia wheel is moved to one of said different switch positions.

6. A switch structure comprising a stationary switch structure and a rotary switch structure, said stationary switch structure comprising: a case having front, top, rear, and bottom wall members and a transverse wall member extending between the aforementioned four wall members, said five wall members of said case constituting a unitary rigid structure; an end plate mounted on each end of said switch case to close the sides of said switch case; interengaging members formed in the switch case which are designed to mate with corresponding interengaging members formed in the end plates in order to accurately align the end plates and the switch case and to prevent movement of the end plates and the switch case with respect to each other about a horizontal axis parallel to said front wall; said transverse wall member providing a recessed well on one side thereof and a corresponding cylindrical protrusion on the other side thereof; said front wall member having an open window section opposite said cylindrical protrusion; a bore in the center of the well; a printed circuit plate composed of insulating material mounted opposite said well and having first electrical contacts formed thereon, said printed circuit plate having an aperture formed in the central portion thereof and notches formed on the sides thereof, said printed circuit plate and said first contacts projecting rearwardly from said front wall; a cover plate mounted between one of said end brackets and said printed circuit plate, said cover plate having pins formed on the inner side thereof which project through corresponding holes formed in said transverse wall member and which engage said notches and said central aperture of said printed circuit plate in order to align said printed circuit plate and to hOld said printed circuit plate against said transverse wall member, said cover plate being permanently mounted in position by heat staking said cover plate pins on the opposite side of said transverse wall member; said rotary switch structure comprising: a rotatable brush wheel mounted in said well and bearing second electrical contacts facing and engaging the first contacts on said printed circuit plate; a rotatable indicia wheel encircling said cylindrical protrusion, said indicia wheel being connected to said brush wheel by shaft means extending through said bore whereby said indicia wheel and said brush wheel are adapted to rotate together; said indicia wheel bearing different symbols on its periphery corresponding respectively to different switch positions, a selected one of said symbols being registered in an indicia indicating position where it is visible through said window when the indicia wheel is moved to one of said different switch positions; said indicia wheel also bearing a plurality of radially extending finger lugs on its periphery, successive ones of which are spaced apart by an amount sufficient to receive the distal portion of an operator''s finger, at least one lug of said wheel projecting at any one time radially outward through said open window whereby said lug is accessible from the front of said switch for operation by the finger of the user; the top and bottom walls of the switch case and the end plates having a recessed portion extending around the outside of the switch structure; two ridges formed on each end plate in said recessed portion, said ridges being spaced from the end of each end plate and extending the full width of said recessed portion but being narrow compared with the height of said end plates; and two identical U-shaped bands adapted to lie within said recessed portion and together to embrace the switch structure and to secure the parts of the switch structure together.