GB2071608A - Releasable holding device between a holding arm and a support of a hand-operated apparatus - Google Patents

Abstract

A releasable holding device between a holding arm (4) and a support (1) of a hand-operated apparatus comprises two parts (2, 3) in releasable centering engagement with a resilient holding means therebetween in the form of at least one magnet (19, 20). The magnet means, whether permanent magnet or electromagnet, is preferably disposed on a circle centred on the axis of the device with a safety switch (22) positioned on this axis, although the provision of such a switch is not mandatory. <IMAGE>

Description

SPECIFICATION Releasable holding device between a holding arm and a support of a hand-operated apparatus This invention relates to a releasable holding device between a holding arm and a support of a hand-operated apparatus, the device comprising two parts in a releasable centering engagement which are held together by resilient holding means.

Such releaseable holding devices are used as over-load protection devices. For example, a tool or some other working implement is arranged on the holding arm of the hand-operated apparatus; within the holding device there is positioned, between the two parts, a switch which can be actuated by a relative movement between the parts and which causes a disconnection of the drive of the apparatus. Such a switch is included in a preferred design of the device in order to create a safety device. However, the invention also includes a holding device which is releasable and makes possible an exchange of tools or working or gripping implements; however, even with this arrangement, a safety switch is preferably included.

Such overload protection devices are known from published West German patent application 27 17 871 in which the two parts are formed respectively as a cup-shaped receiver and as a disc with a curved edge movable within the receiver. All known or future designs of the two device parts are to be considered as included within the scope of the present invention, i.e. both an unreleasable arrangement between relative movable parts and also parts which are separable from one another, i.e. which can be raised one from the other.

In the known devices it is conventional to use at least one spring as the flexible holding means. The possibility of providing a plurality of springs arranged around a circle is also known. The use of springs has the disadvantage that in practice one has a suspension which tends to oscillate. In this connection the provision of mutual buffers is of particular significance, but this makes the devices expensive. In addition, problems arise with the use of a plurality of springs because of the fact that their characteristics are not always uniform. This means that in a device of the basic type with which we are concerned here one spring may be permanently subjected to greater stress than another spring.

With the use of springs there is also the disadvantage that not only is a compression possible but also a unilateral tilting, so that effects of greatly differing form can arise in spite of the maintenance of a defined connecting force between the parts.

Furthermore, particularly in connection with a holding device which serves for the exchange of tools or other implements, the use of a spring is disadvantageous since it must be anchored reliably to both parts. It is therefore comparatively time-consuming to carry out the exhange or replacement procedure.

It is an object of the present invention to embody a resilient holding means in a holding device of the type first referred to above, in such a way that in a defined manner there is a release upon loading of the device beyond a threshold value and to a certain degree a relative movement between the two parts takes place, in which case then the holding force is completely cancelled.

This object is achieved in accordance with the present invention by the holding means comprising at least one magnet.

A magnet has the advantage that the elements of the magnetic circuit can be provided spaced from one another on the different parts of the device, formed possibly as housing parts of hollow shells, including an arrangement in which at least one magnet is arranged on one of the parts and at least one armature for the completion of a magnetic circuit is arranged on the other part.

When the parts of the holding device move relative to one another, under the influence of forces exerted on the holding arm or on the tool, this results, depending upon the strength of the magnets, which is adjustable or can be chosen for a particular application, in the possibility of a movement which can be controlled by the keyed configuration of interengaging profiled areas between the two parts. As a result of this movement, which can take place in the transverse or axial direction while at least initially maintaining the magnetic coupling, the magnetic circuit is eventually broken upon the extent of the movement exceeding a limit value, so that the holding force is abruptly broken and the parts which are in engagement with one another are freed.

According to a preferred embodiment of the invention a magnet ring arrangement is provided between the parts, so that thereby in the compressed state of the holding device there is annular contact between the elements of the ring magnet arrangement and consequently a definite support which is not therefore subject to oscillation in the compressed condition. Moreover, a ring magnet arrangement, whether continuous or composed of individual magnets, also creates the possibility of a certain rotational adjustment by having alternate magnetic poles in the magnet array.

In one preferred embodiment permanent magnets are used. This leads to a simple construction. Moreover, the permanent magnets can easily be exchanged or replaced so that the releasable holding device can be adapted as required for a particular purpose or type of tool which is mounted on the holding arm.

According to another preferred embodiment an electromagnet or electromagnets are used having an energising winding(s) connected to a source of energy by way of a control circuit. The control circuit can include a switch within the holding device, so that a safety device is thereby also created. A switch externally of the holding device makes it possible to switch the electromagnets on and off selectively, so that the exchange or replacement procedure is made easier. With the use of electromagnets, in a preferred arrangement, at least one regulating element is arranged in the control circuit and is adjustable in dependence upon the operating conditions of the device. By this means the device can be adapted to particular requirements without great expense.

The operating conditions can specify loading limits, these being dependent upon the particular working processes. For example, in this connection, the weight of tools which can be guided by the hand-operated apparatus can be included. There is therefore a particular advantage in being able to adapt the control circuit.

In one preferred embodiment co-operating magnet elements with profiled pole shoes are provided which are arranged to come into centred engagement. The engaging profiled areas are here produced as part of the magnetic circuit, which simplifies the structure of the device. This also makes is possible for a keeper element with a correspondingly opposite profile to be used.

In a preferred arrangement, such profilings are formed as wedging surfaces in the form of wedges and grooves arranged in a radially symmetrical format, possibly as axially symmetrical crown teeth if a ring magnet arrangement is used. In this particular case the parts of the device may be formed as housing shells with a circular or polygonal circumferential shape, with the peripheral flanges being formed directly by magnet elements. However, also included is the adaptation of the or each of the magnetic circuits as hollow shell parts supported on one another at their edges and which additionally protectively encircle the magnet arrangement.

In one preferred construction, the two device parts are formed in the manner of a magnetic clutch whose housing parts have radially symmetrical profilings of keyed configuration.

Particularly with the use of permanent magnets, these may advantageously be provided with compensation winding means which can be switched into circuit in dependence upon movement between the parts. In this way the release of the parts is improved.

In another preferred arrangement, at least three magnets are arranged equi-spaced around a circle centred on the axis of the device and at least one switch is provided within this circle. A central positioning of the switch is preferred, in order thereby to achieve a uniform switch actuation for any possible movement of the parts.

In order that the invention may be fully understood, a number of embodiments of holding device in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a sectional side view of a first embodiment of releasably holding device formed as an overload protection device; Fig. 2 is a sectional side view of a second embodiment of holding device; Fig. 3 is a plan view of the device shown in Fig.

2, being a section taken along the line Ill-Ill of Fig. 2; and Fig. 4 is a view, corresponding to that of Fig. 2, but of a third embodiment of holding device.

In Fig. 1 there is shown a receiver constituting one part 2 of the holding device and mounted on a support 1. An element 3 which constitutes the other part of the holding device is mounted for movement relative to the receiver, and to this other part 3 is connected an arm 4 which constitutes part of a hand-operated apparatus.

In this embodiment shown in Fig. 1 the part 2 comprises a base plate 5 and a cup-shaped housing 6 extending above the base plate and having inwardly directed projections 7 and 8 forming a circumferential flange 9. The projections 7 and 8 or the flange 9 define a central aperture 10 through which extends a neck 11 of the part 3 with freedom for play. The part 3 includes a plate 12 externally of the housing 6 and above the neck 11. The neck 11 extends down through the aperture 10 into the housing 6, and within the housing, it carries a star 13 or, in a completed state, a corresponding plate. Three frusto-conical holes are formed through the flange 9, two of which are shown in Fig. 1 at 14 and 15. These three holes are spaced uniformly around the circumference of the device and each tapers inwardly towards the outside of the housing 6.

Conical detents, e.g. 1 7 and 18, which have a cross-section which narrows from the base plate 5 of the housing towards plate 12 engage in these holes 14, 1 5 which serve as countersinks and which are aligned with the central axis of the housing 6. The detents 17 and 18, with which a corresponding third detent is also associated although not shown in Fig. 1, are secured to the plate or star 1 3 so that this plate is held spaced from the flange 9 when the detents and countersinks are in engagement.

A magnet arrangement 19, which constitutes a resilient holding means, is provided between the projections 7 and 8 or the flange 9 on the one hand and the plate or star 1 3 on the other hand.

The magnet arrangement 1 9 for example comprises keeper elements arranged in a ring around the central aperture 10 and permanent magnets 20 arranged correspondingly on the plate or star 13. The permanent magnets 20 are suitably arranged to be of alternating poiarity at their upper surfaces in the circumferential direction of the annular array. By this means the parts 2 and 3 are held so that with engagement of the detents 17, 18 in the holes 14, 1 5 they are capable of axial movement relative to each other, although above all with such engagement there is an inflexible guidance of the two parts 2 and 3 one relative to the other.

The star 13 has a pin 21 at its underside which is arranged to actuate a switch 22, formed as a safety switch, when the star is urged down into the housing 6.

An axial displacement of the arm 4 causes an inward movement of the star 13 and actuation of the switch 22. However, it will also be appreciated that simultaneously with this the tapering detents 17, 18 are given a degree of play in the tapering holes 14, 1 5 in which they are seated.

Consequently, a lateral movement of the arm 4 is possible after an inward movement of the arm has taken place for the actuation of the swtich 22. If a force is exerted on the arm 4 in a sense to cause a lateral movement, then the tapering nature of the conical detents 1 7, 1 8 in the tapering holes 14, 15 ensures, because of the wedging effect, an inward movement of the star 13 and consequently an actuation of the switch 22. When such an inward movement takes place, the elements of the magnet arrangement 1 9 are moved apart until the magnetic circuit is broken and a release takes place.

The spacing between the pin 21 and a switchactuating member 25 of the switch 22 can be so chosen that the switch is actuated before the magnetic circuit is broken. A reliable actuation under all circumstances is guaranteed for the illustrated embodiment by for example providing a plate-type abutment 23 on the switch-actuating member 25.

It is pointed out that with this arrangement at least three conical detents are provided in order to ensure a uniform mounting.

Fig. 2 shows a holding device consisting of two parts 26 and 27 which are formed for example as hollow shells, possibly cup-shaped, and are associated with one another so that upstanding peripheral flanges 28 and 29 of the respective parts engage one another. As can be seen from Fig. 3, the two parts of the device are circular when viewed in plan. However, a polygonal configuration is alternatively possible.

A base plate 30 of the lower part 26 is carried for example on a support 1, and a base plate 31 of the upper part 27 is carried on the arm 4.

The peripheral flanges 28 and 29 are provided with profilings 32 and 33 formed as keys and keyways or wedges and grooves arranged radially symmetrically relative to the central axis 34. In the case of a slim arrangement these profilings could be formed as radial serrations arranged side-byside.

Magnets 35, 36 are provided as the resilient holding means, as can additionally be seen from Fig. 3. If these magnets 35, 36 are formed as permanent magnets, then the poled magnet elements 37, 38 are arranged within cup-shaped keeper rings 39, 40 which are provided on the lower part 26 of the device and which are associated with armatures 41,42 on the upper part 27. These magnets are preferably mounted in a circular array. At least two such magnets are provided. Also included is an arrangement in which a crown ring magnet with alternating magnetic poles is arranged concentrically about the central axis 34.If individual magnets 35, 36, whether in the form of permanent magnets or electromagnets are used, then an arrangement as shown in Fig. 3 is included within the scope of the invention in which four such magnets 35, 36, 43, 44 are provided concentrically about the central axis 34. With such an arrangement a central switch corresponding to the switch 22 of Fig. 1 can be provided. With the arrangement according to Fig. 2, however, the base plates 30, 31 are penetrated centrally by tubular members 45, 46 which rest upon one another by means of respective flanges provided with sealing means therebetween in the engaged position within the two parts 26,27 of the device.These tubular members 45, 46 are provided so that actuating members for the operation of a tool can pass through. i.e. especially tubular or hose connections for pneumatic or hydraulic pressure means. In this case, instead of a central switch 22 according to Fig. 1, at least three contact switches, such as 47, 48, 49, 50, are arranged around the circumference. These contact switches are preferably connected in series. This then means that the lifting of even one contact switch out of contact because of a displacement of the interengaged radial serrations which form the profilings 32, 33 will cause a switching-off to occur.It is alternatively possible that the switches 47 to 50 can be connected in parallel in part, in order that a switching-off then first occurs only after a predetermined displacement in the circumferential and/or axial direction has taken place. The magnet arrangement has the advantage that a break, i.e. a release of the holding force, occurs with certainty after a predetermined limited separation of the magnet elements which are coupled to one another.

It will be appreciated that the magnets 35, 36 could alternatively be formed as electromagnets with an energising circuit arranged in the usual way, as is illustrated in greater detail in Fig. 4. In Fig. 2 the possibility is shown that with the arrangement of the magnets 35,36 as permanent magnets using the magnet elements 37, 38 compensation windings 49, 50 only schematically shown in the drawings, may be provided by means of which, using control circuits which are not shown in detail, a contrary energising force can be generated to cancel the holding force. This is a particular advantage of the magnetic holding, because any faulty action which occurs and by which a contact (not shown) may be actuated, can bring about a release of the overload protection device. For further explanation of this, an energising circuit for the compensation windings 49, 50 is shown.This energising circuit 51 comprises a source 52 of energy and a switch 53 which, as indicated by the arrow 54, can be actuated by a control in accordance with a preselected influence. In practice, compensation windings are arranged correspondingly to the energising windings shown in Fig. 4, but with reversed flux directions at the pole pieces.

The radial teeth of the profilings 32,33 can be seen from Fig. 3, and from their directions it can be seen that no lateral displacement of the two parts 26, 27 of the device relative to one another is possible without axial movement of the parts 26, 27 apart.

It will be appreciated that the magnets 37, 38, especially the magnet pieces, can be formed as electromagnets. This is indicated in Fig. 4 by the windings 55, 56 which are connected to electrical leads 57, 58. By this means it is possible to switch a control circuit in dependence upon particular operating conditions.

The switch 22 which is arranged centrally in this embodiment is connected by means of electrical leads 59 to a driven circuit of the handoperated apparatus. In Flg. 4 a helical restraining strip 60 is shown which is secured at each end to fastening eyes fitted into the upper and lower parts 26 and 27 respectively of the device. Such a restraining strip can also be provided in the other embodiments.

According to Fig. 3, with the provision of four switches 47 to 50, diagonally opposed switches can be connected together in switching circuits, with the result that one switch pair can act as a safety switch and the other switch pair as a signalling switch. According to Flg. 3, the switches 47 to 50 are connected in sequence one after the other as signal switches in a circuit 61 which includes an electrical regulating or signalling device 62.

The described embodiments have the advantage of simple construction without movable parts for the creation and release of the coupling, as well as a sensitive response to torques and transverse forces in all directions. It is also a feature that the centering engagement of the profilings between the two parts of the device comes about through the axial movement controlled bythe configuration of the profilings and also through a varying influence on the holding force which is dependent upon the magnetic attraction forces.

One particularly advantageous embodiment of the device is the formation of the device as a cup magnet with a central magnetic core, with the peripheral flange or flanges being used as a keeper element or elements. Cup-shaped magnets are already shown in principle in Figs. 1 to 4 if one considers the individual magnets. This latter embodiment thus envisages the structuring of the whole device as a cup-shaped magnet, in which this cup-shaped magnet with its peripheral flanges forms one part and the other part is formed either as a plate or with an angled peripheral flange.

For this arrangement the use of an electromagnet is allowed for if the core is encircled by an energising coil.

Claims (13)

1. A releasable holding device between a holding arm and a support of a hand-operated apparatus, the device comprising two parts in releasable centering engagement which are held together by resilient holding means, in which the holding means comprises at least one magnet.

2. A device as claimed in claim 1, which includes a magnet ring arrangement between the said parts.

3. A device as claimed in claim 1 or 2, in which said at least one magnet is a permanent magnet or magnets.

4. A device as claimed in claim 1 or 2, in which said at least one magnet comprises an electromagnet or electromagnets having an energising coil or coils connected to a source of energy by way of a control circuit.

5. A device as claimed in claim 4, in which the control circuit includes at least one regulating element which is adjustable in dependence upon operating conditions of the device.

6. A device as claimed in any preceding claim, which includes co-operating magnet elements with profiled pole shoes which are arranged to come into centering engagement with each other.

7. A device as claimed in any preceding claim, in which the parts of the device are formed as housing shells and define peripheral flanges formed directly by magnet elements.

8. A device as claimed in any of claims 1 to 6, in which the two parts are formed as a magnetic coupling having housing parts which include radially symmetrical profilings of keyed configuration.

9. A device as claimed in claim 3 or 4, in which said at least one magnet, particularly if formed as a permanent magnet or magnets, is provided with compensation winding means which can be energised in dependence upon a movement between the two parts.

10. A device as claimed in claim 3 or 4, in which at least two magnets are arranged spaced around a circle centred on the axis of the device, and at least one switch is positioned within this circle.

11. A device as claimed in any of claims 3 to 5, which includes a plurality of switches formed as contact switches and spaced around a circle, the switches being connected in pairs with at least one of the switches being connected into a circuit which includes a regulating or signalling device.

12. A device as claimed in any of claims 1 to 6 or 8, formed as a cup-shaped magnet with a central magnetic core, and with a peripheral flange or flanges formed as a keeper element or elements.

13. A releasable holding device substantially as hereinbefore described with reference to Fig. 1, Figs. 2 and 3, or Fig. 4 of the accompanying drawings.