WO1998058870A1

WO1998058870A1 - Vacuum lifter system

Info

Publication number: WO1998058870A1
Application number: PCT/DK1998/000258
Authority: WO
Inventors: Lasse Godtfred Juel
Original assignee: Lasse Godtfred Juel
Priority date: 1997-06-20
Filing date: 1998-06-18
Publication date: 1998-12-30

Abstract

In connection with the use of a hoisting system of the dynamical suction lifter type, i.e. comprising a hose bellows connected with the suction side of a suction blower and having an operator controlled intake valve for outer air for regulating the degree of contraction of the bellows at the occurring resulting suction pressure, it is customary to dimension the system components, in particular the diameter of the hose bellow and the driving motor of the suction blower, for adaptation to the rather narrow weight range that is actual for typically transferred objects, e.g. between a belt-conveyor and a piling pallet. For enabling a well graduated regulation the suction contraction must be neither too large nor too small. With the invention it has been realized that with the use of one same hose bellows and one same driving motor it is perfectly possible to handle objects in more different weight ranges, viz. by a suitably adjusted suction capacity of the suction blower by means of a variable driving gear or - preferably a controllable frequency adaptor for the supply current to the motor.

Description

Vacuum Lifter System

The present invention concerns a dynamic suction lifter of the type which comprises a flexible hose bellows which at the one end is connected to a vacuum source, and at the other end is provided with a suction head or possibly another and purely mechanical lifting arrangement, and an operator-controlled valve for the controlled induction of air directly to this end of the hose bellows, i.e. independently of the suction from a possible suction head, respectively with means for operative discontinuation of the suction at such a suction head or for the releasing of the lifting engagement of the mechanical lifting arrangement.

The hose bellows shall primarily be considered as a controlled lifting arrangement which operates pneumatically, in that by operation of said valve it will contract at a high vacuum occurring at the suction source, i.e. by closing or only slight opening for the intake of outer air, while under the influence of an overhead load or by its own weight or elasticity it will expand when the valve is opened for the intake of a great amount of outer air, since the effective vacuum or suction on the hose bellows will thus be weak. Therefore, it is possible by means of the valve to control the length of the hose bellows and thus to hoist a gripped load up and down for the re-positioning of the load, e.g. between the end of a conveyor belt and different stacking positions on a pallet.

This effect is independent of the volumetric orientation of the hose bellows, in that e.g. it can be operative while lying horizontally if its free end is connected to a hoisting wire hanging down from a reversing wheel. However, the terminology chosen in the following is one which refers to a simple, hanging-down orientation of the hose bellows. The possible use of a suction head as lifting means on the hose bellows is of secondary importance, in that there is herewith involved only an expedient further utilization of the suction effect which, however, is without importance for the conditions regarding the controlling of the longitudinal movements of the hose bellows.

In practice it is necessary to work with a suction source, normally a so-called side-channel blower, which is dimensioned in relation to the weight range of the items to be handled, whereby the diameter of the hose bellows must also be taken into consideration, partly with regard to the lifting capacity and partly with regard to the control capacity. It is already obvious that the source of suction must be sufficiently strong to be at all able to effect the lif- ting of a load within a relevant weight range. For example, it will typically apply that a blower which is driven at 3000 rpm will be suitable for the lifting of loads of 10-20 kg with a hose bellows diameter of 120 mm, whereas with a hose diameter of 180 mm it is suitable for loads of 30-70 kg. Cor- respondingly, with a hose diameter of 120 mm, a blower which is driven at 6000 rpm could be used for loads of 30-40 kg, and for loads of 70-100 kg with a hose diameter of 180 mm. Suitable intermediate ranges can be attained with an rpm of 4-5000 and a hose diameter of 140-160 mm respectively. It is immediately understandable that work can hereby be carried out with diverse upper limits for the possible weight of the loads to be handled, but in fact the stated lower limits are of equal significance. The situation is namely that if an "over-strong" suction occurs in relation to loads in a given weight range, it becomes difficult for the operator to control vertical movements of the lower end of the hose bellows, in that at a relatively very strong suction a light item can easily be sucked right up to the top immediately, without the operator being able to precisely control the lifting by means of the regulating valve, and perhaps even without the load being able to be lowered with full opening of this valve.

In light of this, a practice has been developed with which the technical solution is carefully adapted to suit the individual cases of use, and where regard is also paid to the choice of hose diameter, motor and blower with associated upper and lower limits for the weight loading of the hose bellows. In practice, it is herewith possible to operate with only 3-6 different types of apparatus.

However, productions arise with which it is current to handle items within widely different weight classes, and with the invention it is intended to provide a transfer unit which finds more general application in connection with loads in different weight classes, especially for ensuring that operations can be carried out with sufficiently high suction capacities for the lifting of heavy goods, and yet in the handling of light goods of maintaining the possibility of being able to control the lifting/lowering of these goods in a well-controlled manner.

With the invention it has been found that in actual fact it is possible to accommodate a very wide range of weight intervals with the use of an apparatus which has a mo- tor/blower/hose diameter adapted for the handling of items in the highest occurring weight class, and which moreover has a control arrangement such as a frequency converter which enables the speed of the motor to be reduced for different underlying weights, each representing an operation interval. In the ideal case, the speed of the motor should be regulated in accordance with the precise weight of the item to be handled, but this would thus require both a precise indication of the weight of the item and a precise regulation of the motor power, which will also place qualified demands on the operator. Therefore, a preferred solution is for use to be made only of rough regulation intervals, e.g. precisely those corresponding to the capacity of the above-mentioned 3- 6 different types of apparatus. Normally, the operator will hereby not have any special difficulties in adjusting the apparatus to suit the relevant task, in that use can be made e.g. of a simple setting scale which merely refers to quite few different weight classes, without more detailed definitions regarding actual weight or motor revolutions. It is important to note that it has been found possible to work in an operational economic manner merely by using a reduction in the speed of the motor, and moreover without any other changes in the motor, the blower, the hose diameter or the operating-valve arrangement on the hose bel- lows.

An example of an arrangement according to the invention is shown in the drawing, which is a schematic illustration of an apparatus in connection with a transfer between a conveyor 2 and a support pallet 4 for items 6 transpor- ted on the conveyor 2. The transfer apparatus comprises a motor 8, a suction hose 12, a suction blower 10 and a lifting hose 14. The latter is suspended in a displaceable manner in a slide rail 16, and is provided at its lower end with a valve housing 18 with an air intake and an associated control handle 20, and with a lower suction head 22 for the gripping of the items 6. This suction head could well be replaced by other lifting means such as a hook, in that the primary function of the occurring suction is not to apply suction to the items, but to enable the length of the suction hose to be changed under control from the operating handle 20, i.e. by changing the suction pressure in this hose as a function of more or less outer air being inducted through the valve housing 18. When the operator opens for full air intake by means of the handle 20, the suction pressure in the hose bellows 14 will fall so much that the lower end of the hose will move downwards towards an almost fully axially-extended con- dition, i.e. the gripping head 22 will be lowered until it reaches the item 6. After the item has been gripped, the gripping head and herewith the item can be raised in a controlled manner by operating the handle 20 for reduced air intake, whereby a higher suction pressure is built up in the hose bellows 14, and with a certain degree of practice the operator can hereby hold the lifted item suspended at a suitable transfer height, so that the item can be transferred to a stacking position on the pallet 4 by displacement of the hose 14 along the slide rail 16, and with a subsequent re- lowering operation by the axial extension of the hose 14. For a given plant, the above-mentioned "suitable transfer height" will be determined by the degree to which the intake valve is opened in relation partly to the effect of the suction blower 10 and partly the weight of the lifted item 6. With a plant which traditionally is suitably dimensioned for the handling of items 6 within a certain weight range, the occurrence of a relatively very light item will result in the capacity of the suction blower being so superior that it will draw the gripping head 22 all the way to the top, without leaving the operator with any practical possibility of regulation. On the other hand, in the event of an "over-heavy" item, the suction capacity of the blower can be so low that the item cannot be lifted at all, or at any rate not lifted sufficiently to enable it to be transferred to a suitably high stacking position on the pallet 4.

While it has hitherto been assumed that it has hereby been necessary to dimension various plants for items of different weight classes in order to achieve both economical operation and easy operability, in connection with the inven- tion it has actually proved possible to meet both of these requirements with one and the same plant, i.e. by dimensioning this for the handling of the heaviest items which can be expected, and moreover by equipping the plant to operate with a stepless or gradual reduction of the suction blower' s capacity by means of a suitable controllable gear mechanism, or by controlling the speed of the motor 8 for regulation of the rpm of the rotor in the blower 10. In practice, work can hereby be carried out with quite few operation ranges, prefe- rably 3-5 ranges, and it has proved to be fully sufficient and expedient for the changeover to be effected solely by controlling the frequency of the motor 8 by means of a simple control box 24 placed reasonably close to the operator. The motor can hereby work in an economic manner also in the lower speed ranges. However, the invention is not limited to the suction capacity of the blower having to be regulated in precisely this manner.

If the operator is in doubt concerning the relevant setting in connection with a given item, a suitable interme- diate suction capacity can be selected which can then be reduced or increased all depending on whether the item is raised too violently or not raised at all.

Claims

C L A I S

1. Hoisting system of the dynamical suction lifter type with a flexible hose bellows which is connected to the suction side of a suction blower, and has a supported end part and an opposite free end part which is in tractive or supporting connection with a gripping element for releasable lifting of items, said hose bellows being connected to an operating valve which enables an operator-controlled, gradual induction of outer air for the regulation of the effective suction pressure in the hose bellows, and herewith their degree of axial contraction, characterized in that the drive arrangement for the suction blower is configured with regulation means which enable operator-controlled regulation of the suction capacity of the blower.

2. Hoisting system according to claim 1, characterized in that the regulation means can be operated for adjustment of the suction capacity of the blower in a stepless manner.

3. Hoisting system according to claim 1, characterized in that the regulation means can be operated for the adjustment of the suction capacity of the blower through only 3-6 steps.

4. Hoisting system according to claim 2 or 3 , cha- racterized in that the regulation means co-operate with a frequency converter for the suction blower's drive motor.