GB2040396A

GB2040396A - Securing a control knob to a shaft

Info

Publication number: GB2040396A
Application number: GB8001487A
Authority: GB
Original assignee: BRETER SpA
Current assignee: BRETER SpA
Priority date: 1979-01-26
Filing date: 1980-01-16
Publication date: 1980-08-28
Also published as: DE3001196A1; BR8000425A; FR2447596A1; DE3001196C2; ES255479U; IT7920629V0; GB2040396B; MX147360A; ES255479Y; GR66006B

Abstract

An electrical component 1 such as a switch has a rotatable spindle 3 of polygonal cross-section fitting through a hole 5 in a mounting panel 4, to which a plate 6 is fixed, using holes 12. Plate 6 carries a disc 7 on which operational reference data is shown through a transparent cover 8, with coaxial holes 9, 10, 11. Spindle 3 engages in a similarly polygonal shaped axial cavity 14 in a control knob 13 which can be used to rotate the spindle. A ring portion 16 formed on the knob has diametrically opposed circular segmental protrusions 17, 18 which become engaged in recesses 19 disposed around the hole 9 so that the knob can rotate but cannot be pulled axially off the spindle unless the protrusions are disengaged from the recesses by a lever action of a pointed-end tool inserted in slot 22 in the ring. Alternatively, a recessed rotatable flanged bush (20) behind panel 4 may replace plate 6. <IMAGE>

Description

SPECIFICATION A control knob for electrical equipment This invention relates to a control knob, for electri cal equipment, for example commutators, switches or the like, the knob having an axial cavity of polygonal cross section to receive a rotary drive shaft of the equipment so that the shaft is integral with the knob during rotary motion.

Presently adopted systems designed to secure a control knob to such aforementioned electrical equipment, provides forth clamping of the knob directly to the drive shaft.

One of such systems includes a screw which, going through a threaded hole in the knob, connects the knob to the drive shaft by the screw either pressing on the shaft pressure on same or engaging in a threaded hole in the shaft.

In another known clamping system, the drive shaft has an end portion of semicircular cross-section.

This end portion protrudes from the equipment and engages in a cavity of corresponding cross-section in the knob. To prevent accidental removal of the knob by sliding thereof along the shaft, the cavity is provided with elastic components designed to clamp against the shaft to produce the necessary friction to make the knob and shaft integral.

Providing the knob with screws or elastic clamping components adds to manufacturing and assembly costs.

According to the invention there is provided a control knob for electrical equipment, for example commutators, switches or the like, said equipment having a rotary drive shaft of polygonal crosssection, said knob comprising an axial cavity having a polygonal cross-section to receive the drive shaft which is integral with the knob during rotary motion, and a continuation of said axial cavity being provided by a ring-shaped extension having an outside edge provided, symmetrically in relation to a medium longitudinal plane of the knob, with at least two protrusions which fit into corresponding fixing components provided on an accessory component of said electrical equipment.

The ring-shaped extension on the knob can be equipped with a radial slot in which one can fit a tool tip in order to release the knob.

The invention will now be further described, by way of example, with reference to the accompanying drawing in which: Fig. 1 is an exploded view partly in section of an item of electrical equipment and a control knob formed according to the invention, and Fig. 2 is an exploded view partly in section showing the knob in Fig. 1 in combination with a guide bush by which the knob can be attached to electrical equipment.

With reference to Fig. 1, an item of electrical equipment, for example as a commutator or a switch, is shown at 1 having a body 2 from which protrudes a rotatable drive shaft 3 having an end portion of polygonal cross-section.

A panel 4 is designed to support the electrical equipment 1. The panel 4 is formed with a through hole 5 into which the end portion of the drive shaft3 is fitted until the body 2 comes into contact with a side of the panel. The opposite face of the panel 4 is provided with a support plate 6 for a data plate 7 presenting some operational reference data visible through a cover 8 made of transparent material and preset for fixing to the support plate 6 by known clamping components (not shown).

The support plate 6, the data plate 7 and the cover 8, are formed with respective holes 9, 10 and 11 which all coincide with the hole 5.

The support plate 6 is also formed with a number of holes 12 to allow the passage of screws (not shown) for clamping the support plate 6 to the panel 4 and to the equipment 1.

A control knob 13 has an axially extending cavity 14 of polygonal cross-section to receive the corresponding polygonal cross-section shaped end portion of the drive shaft 3.

As a continuation of axial cavity 14, a ring-shaped extension 16 protrudes from base 15 of the knob 13.

An outside edge of the extension 16 is provided, symmetrically with respect to a median plane of the knob, with two protrusions 17 and 18 each of a circular segmental shape.

The protrusions 17 and 18 make it possible for the knob to clamp onto support plate 6 which is provided, inside the edge of the hole 9, with a number of reliefs 19 arranged around a circumference which is concentric with the hole 9. The reliefs 19, which are fixing components of the knob 13, prevent axial movement of the knob away from the shaft 3 but allow the knob to rotate freely around its axis.

In order to permit release of the knob 13, the ringshaped extension 16 has a radial slot 22 designed to allow the insertion of a tool tip (not shown) into the slot so that the tool be employed as a suitable lever.

With reference to Fig. 2, a guide bush 20 is provided instead of the support plate 6 (Fig. 1) in those applications where either the operational reference data is provided directly on the panel 4, or the data plate 7 is secured to the panel 4. In order to keep the knob 13 linked to the panel 4, the bush 20 is provided on its internal surface with a number of reliefs 21 which are simiiar to the reliefs 19 (Fig. 1).

Particular advantages obtained using a knob as described above with reference to the drawing consists, first of all, in the absence of components, such as screws, tongues or rings, for fastening the knob to the drive shaft. Secondly, the knob allows quick and easy coupling in response to simple pressure applied along the axis of the knob towards the shaft 3. On the other hand, one should also note that the knob cannot be released by simply pulling the knob.

Instead it is necessary to employ a pointed tool to act as a lever. Thus there is little chance of accidental releases of the knob due to wear or other causes.

1. Acontrol knob, for electrical equipment for example commutators, switches or the like, said equipment having a rotary drive shaft of polygonal cross-section, said knob comprising an axial cavity having a polygonal cross-section to receive the drive shaft which is integral with the knob during rotary motion, and a continuation of said axial cavity being

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A control knob for electrical equipment This invention relates to a control knob, for electri cal equipment, for example commutators, switches or the like, the knob having an axial cavity of polygonal cross section to receive a rotary drive shaft of the equipment so that the shaft is integral with the knob during rotary motion. Presently adopted systems designed to secure a control knob to such aforementioned electrical equipment, provides forth clamping of the knob directly to the drive shaft. One of such systems includes a screw which, going through a threaded hole in the knob, connects the knob to the drive shaft by the screw either pressing on the shaft pressure on same or engaging in a threaded hole in the shaft. In another known clamping system, the drive shaft has an end portion of semicircular cross-section. This end portion protrudes from the equipment and engages in a cavity of corresponding cross-section in the knob. To prevent accidental removal of the knob by sliding thereof along the shaft, the cavity is provided with elastic components designed to clamp against the shaft to produce the necessary friction to make the knob and shaft integral. Providing the knob with screws or elastic clamping components adds to manufacturing and assembly costs. According to the invention there is provided a control knob for electrical equipment, for example commutators, switches or the like, said equipment having a rotary drive shaft of polygonal crosssection, said knob comprising an axial cavity having a polygonal cross-section to receive the drive shaft which is integral with the knob during rotary motion, and a continuation of said axial cavity being provided by a ring-shaped extension having an outside edge provided, symmetrically in relation to a medium longitudinal plane of the knob, with at least two protrusions which fit into corresponding fixing components provided on an accessory component of said electrical equipment. The ring-shaped extension on the knob can be equipped with a radial slot in which one can fit a tool tip in order to release the knob. The invention will now be further described, by way of example, with reference to the accompanying drawing in which: Fig. 1 is an exploded view partly in section of an item of electrical equipment and a control knob formed according to the invention, and Fig. 2 is an exploded view partly in section showing the knob in Fig. 1 in combination with a guide bush by which the knob can be attached to electrical equipment. With reference to Fig. 1, an item of electrical equipment, for example as a commutator or a switch, is shown at 1 having a body 2 from which protrudes a rotatable drive shaft 3 having an end portion of polygonal cross-section. A panel 4 is designed to support the electrical equipment 1. The panel 4 is formed with a through hole 5 into which the end portion of the drive shaft3 is fitted until the body 2 comes into contact with a side of the panel. The opposite face of the panel 4 is provided with a support plate 6 for a data plate 7 presenting some operational reference data visible through a cover 8 made of transparent material and preset for fixing to the support plate 6 by known clamping components (not shown). The support plate 6, the data plate 7 and the cover 8, are formed with respective holes 9, 10 and 11 which all coincide with the hole 5. The support plate 6 is also formed with a number of holes 12 to allow the passage of screws (not shown) for clamping the support plate 6 to the panel 4 and to the equipment 1. A control knob 13 has an axially extending cavity 14 of polygonal cross-section to receive the corresponding polygonal cross-section shaped end portion of the drive shaft 3. As a continuation of axial cavity 14, a ring-shaped extension 16 protrudes from base 15 of the knob 13. An outside edge of the extension 16 is provided, symmetrically with respect to a median plane of the knob, with two protrusions 17 and 18 each of a circular segmental shape. The protrusions 17 and 18 make it possible for the knob to clamp onto support plate 6 which is provided, inside the edge of the hole 9, with a number of reliefs 19 arranged around a circumference which is concentric with the hole 9. The reliefs 19, which are fixing components of the knob 13, prevent axial movement of the knob away from the shaft 3 but allow the knob to rotate freely around its axis. In order to permit release of the knob 13, the ringshaped extension 16 has a radial slot 22 designed to allow the insertion of a tool tip (not shown) into the slot so that the tool be employed as a suitable lever. With reference to Fig. 2, a guide bush 20 is provided instead of the support plate 6 (Fig. 1) in those applications where either the operational reference data is provided directly on the panel 4, or the data plate 7 is secured to the panel 4. In order to keep the knob 13 linked to the panel 4, the bush 20 is provided on its internal surface with a number of reliefs 21 which are simiiar to the reliefs 19 (Fig. 1). Particular advantages obtained using a knob as described above with reference to the drawing consists, first of all, in the absence of components, such as screws, tongues or rings, for fastening the knob to the drive shaft. Secondly, the knob allows quick and easy coupling in response to simple pressure applied along the axis of the knob towards the shaft 3. On the other hand, one should also note that the knob cannot be released by simply pulling the knob. Instead it is necessary to employ a pointed tool to act as a lever. Thus there is little chance of accidental releases of the knob due to wear or other causes. CLAIMS

1. Acontrol knob, for electrical equipment for example commutators, switches or the like, said equipment having a rotary drive shaft of polygonal cross-section, said knob comprising an axial cavity having a polygonal cross-section to receive the drive shaft which is integral with the knob during rotary motion, and a continuation of said axial cavity being provided by a ring-shaped extension having an outside edge provided, symmetrically in relation to a median longitudinal plane of the knob, with at least two protrusions which fit into corresponding fixing components provided on an accessory component of said electrical equipment.

2. A control knob as claimed in claim 1, in which said fixing components are a plurality of reliefs on a surface defining a through hole in a support for a data plate, and said reliefs are arranged around a circumference concentric with the hole.

3. A control knob as claimed in claim 1, in which said fixing components are a plurality of reliefs on an internal surface of a guide bush.

4. A control knob as claimed in any preceding claim in which characterised by the fact the ringshaped extension of the knob has a radial slot in which a tool tip may be fitted in order to release the knob from said fixing component.

5. A control knob for electrical equipment, for example commutators, switches or the like, said equipment having a rotary drive shaft of polygonal cross-section, said control knob being substantially as hereinbefore described with reference to the accompanying drawing.