GB2227364A

GB2227364A - Pendant switch

Info

Publication number: GB2227364A
Application number: GB8928642A
Authority: GB
Inventors: Harald Bitsch; Heinz Hasselmann; Johannes Kluge; Uwe Lichtenvort; Anton Munzebrock; Klaus-Dieter Oemus; Guenter Somborn
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1988-12-21
Filing date: 1989-12-19
Publication date: 1990-07-25
Also published as: JPH02236920A; GB8928642D0; FR2640608A1; IT1238502B; IT8922587A1; IT8922587A0; CN1045079A

Abstract

A pendant switch for controlling lifting gear has snap acting switching elements 14 disposed in a housing 1, 2 below push-buttons 12 for operating the elements, a handle 3 depending from the housing 1, 2 and the switch being designed and shaped to enable an operator to grip the housing effectively with an index finger in a groove 4, and operate the buttons 12 with a thumb, leaving the remaining fingers free for manipulating a load (Figs. 5-7). Recessing of the pushbuttons between beads (9) (Fig. 2) inhibits inadvertent operation. The handle may have a backwardly extending safety projection 5 for the little finger, and a strain relief tube 17 is screwed over connecting sleeve 8 surrounding electric cables 16. <IMAGE>

Description

PENDANT SWITCH FOR CONTROLLING LIFTING GEAR The invention relates to a pendant switch for controlling lifting gear. Such switches have a housing for at least one switching element operable for example to effect the multi-phase switching of motor currents for induction motors associated with the lifting gear.

The housing also has lower handle, from which adjacent switch actuators for the switching element can be reached by a thumb of the hand of an operator.

A pendant switch of this type is disclosed in US Patent No. 2,348,107, in which the switch-actuating elements are rocker arms which can be thrown upwards and downwards, the operation of which requires great dexterity and concentration. The handle has an indentation for the index finger underneath the housing, although the finger is well suited for grasping a somewhat thicker handle. The housing is also wide, and the thumb cannot grip beyond the width of the housing, as would be desirable for steadying while directing a load which is lifted by lifting gear with nominal currents of up to 12 amperes.

The present invention is directed at a design of pendant switch which is easier to operate. To this end, a pendant switch according to the invention comprises a housing forming a depending handle, the housing enclosing at least one switching element having snap action contacts; and push-buttons for operation by the thumb of an operator's hand, the push-buttons being disposed on the housing proximate the handle and coupled to the switching elements for actuating same. The switching elements are typically of the type having one or two pole switching by simultaneous operation of their snap action contacts.

The push-buttons are normally mounted on a supporting plate between laterally spaced beads on the front face of the housing, with the buttons not projecting past the beads. This inhibits their inadvertent operation. Further, an emergency stop buttion is usually provided, typically disposed over the push buttons on the housing. Such a stop button will normally project above the face of the housing, beyond the beads if the push-buttons are disposed between beads as aforesaid. The preferred emergency stop button is of the type which is operated by being pushed in, and requires rotation to release it for re-use.

Adjacent push-buttons on preferred switches according to the invention can be operated substantially more easily and without special concentration. The switching elements have a small width and are therefore particularly suitable for pendant switches in conjunction with push-button operation. The lateral distance between the push-buttons is narrow, and due to snap action of the switching elements the two switching stages of an actuating element can be felt easily. By locating the push-buttons close together on a relatively narrow housing, the thumb can grip beside the housing while the push-buttons are not being operated.

In another preferred feature of the invention, the housing is formed with a groove on the side opposite the push-buttons for the index finger of an operator's hand. The index finger can thus hold the handle of the pendant switch, so that the other fingers and the thumb of the operator's hand can be used simultaneously for directing a load. Even when a push-button is being actuated, the index finger is sufficient to hold the pendant switch, so that the projecting base of the rear half of the housing and the free fingers can press against the load. This is a particular advantage if a wooden panel for example is being lifted. Then the lifting gear can be controlled by means of the pendant switch, and the panel which is to be lifted can be guided safely with both hands simultaneously.

In another optional feature of the invention, the handle may have a safety projection extending backwards for the little finger on the lower end. The handle may have gripping ribs, a smooth front face and curved back and side faces, so that the correct position in the hand can be felt, as soon as the switch is grasped, without having to look.

The housing of switches according to the invention is normally divided into a front half and a rear half. The front half will usually include at its upper end a tubular connecting sleeve for electric cables to pass through and a strain relief tube which is pushed on. The latter can be made from a reinforced elastomer with threads distributed on its periphery.

This strain relief tube additionally protects the control line from mechanical and chemical influences and damps unwanted oscillation of the freely hanging pendant switch by means of the friction between the line and tube. For mounting the switching elements, the rear half of the housing is removed and the electric cables can be guided to the connection points of the switching elements. The halves of the housing can engage with one another at the safety projection of the handle and then be connected together by means of screws. Then a transition cap surrounding the strain relief tube may be drawn over connection recesses of the parts of the housing.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings wherein: Figure 1 shows a longitudinal section through a pendant switch, Figure 2 shows the side view of the pendant switch, with a view of the switching elements in the right-hand half, Figure 3 shows the section III - III through Figure 2, Figure 4 shows the section IV - IV through Figure 1, Figures 5-7 show a number of possible ways of using the pendant switch.

The housing of the pendant switch is divided into a front half 1 and a rear half 2. This division also extends to the handle 3 as far as the lower safety projection 5, which has on its rear side an insertion point 7 for a lug 21 at the handle end of the rear housing part 2. The handle 3 has circumferential gripping ribs 6 and, at the upper end beneath the rear half of the housing 2, a groove 4 for the index finger.

The front side of the handle is flat, while the side regions and the rear side are curved, as Figure 4 shows.

The front surface of the handle 3 merges into a lateral bead 9 of the front half 1 of the switch housing. The lateral bead 9 encloses a recessed supporting plate 10 for adjacent push-buttons 12 for actuating the snap-action switching element 14. An emergency stop button 13 for an emergency cutout element 15 is arranged above the push-buttons 12. Arrows on the emergency stop button 13 indicate the direction of turning to disengage the pushed-in emergency stop button 13.

The front half 1 of the switch housing has at its upper end a connecting sleeve 8 for electric cables 16 to pass through to the snap-action switching element 14 and the emergency cut-out element 15. A strain relief tube 17 is screwed over the connecting sleeve 8 and is attached by means of a clip 18. A transition cap 19, which firstly surrounds the strain relief tube 17 and secondly is pushed over a connection recess 11 of the two halves 1 and 2 of the switch housing which are connected together by screws 20, is pushed over this attachment point.

There is a seal 22 between the front half 1 and the rear half 2.

Figures 5 to 7 show how the middle finger, ring finger and little finger on the hand operating the pendant switch direct the load, while the index finger holds the pendant switch and the thumb actuates the push-buttons 12 of the switching element 14. Each pushbutton 12 requires continuous depression to activate the lifting gear.

Claims

1. A hand operable pendant switch for controlling lifting gear, comprising a housing forming a depending handle, the housing enclosing at least one switching element having snap action contacts; and push-buttons for operation by the thumb of an operator's hand, the push-buttons being disposed on the housing proximate the handle and coupled to the switching elements for actuating same.

2. A pendant switch according to Claim 1 wherein the housing around the push-buttons and adjacent housing forming the handle are shaped and dimensioned to permit gripping of the handle by the index finger of an operator's hand, and accommodate engagement of the housing by the thumb of a said hand along a side of the housing, leaving other fingers of a said hand free.

3. A pendant switch according to Claim 1 or Claim 2 wherein the housing is formed with a groove on the side opposite the push-buttons for the index finger of an operator's hand.

4. A pendant switch according to any preceding Claim wherein the handle has a safety projection at its distal end for engagement by the little finger of an operator's hand.

5. A pendant switch according to Claim 4 wherein the safety projection is part of the front half of a longitudinally divided housing and has an insertion point for a lug of the rear half of the housing.

6. A pendant switch according to any preceding Claim wherein the handle has gripping ribs.

7. A pendant switch according to any preceding Claim wherein the handle has a smooth front face and curved back and side faces.

8. A pendant switch according to any preceding Claim wherein the housing is divided into a front half and a rear half, the front half having at its upper end a tubular connecting sleeve for electric cables and a strain relief tube push-fitted thereon.

9. A pendant switch according to Claim 8 wherein the halves of the housing are connected by means of screws.

10. A pendant switch according to Claim 8 or Claim 9 wherein the strain relief tube passes through a transition cap which encloses a connection recess of the halves of the housing.

11. A pendant switch according to any preceding Claim wherein the push-buttons are mounted on a supporting plate between laterally spaced beads on the front half of the housing, the buttons not projecting past the beads.

12. A pendant switch according to Claim 11 including in the housing above the push-buttons an emergency stop button for an emergency cut-put element disposed on the housing above the push-buttons.

13. A pendant switch according to Claim 12 wherein the emergency stop button is push operable and thereafter releasable by turning.

14. A pendant switch substantially as described herein with reference to the accompanying drawings.