GB2165796A

GB2165796A - Toggle lever drive in material processing apparatus

Info

Publication number: GB2165796A
Application number: GB08524476A
Authority: GB
Inventors: Helmut Karbach
Original assignee: Adolf Illig Maschinenbau GmbH and Co KG
Current assignee: Adolf Illig Maschinenbau GmbH and Co KG
Priority date: 1984-10-05
Filing date: 1985-10-04
Publication date: 1986-04-23
Also published as: FR2571302A1; DE3436469C1; FR2571302B1; GB2165796B; GB8524476D0

Abstract

Material processing apparatus, such as a sheet moulding machine, Figure 2, or a sheet packaging, or a punching machine, comprises two relatively movable elements (7, 9 and 8, 10) co-operable to process material and a respective toggle lever drive to displace either or each such element. The or each toggle lever drive comprises two cross-members (16, 23) which are relatively movable towards and away from each other and toggle lever linkages (17, 18; 21, 22) to translate relative movement of the cross-members, via pivotally connected links (17, 18), into displacement of the associated one of the material processing elements. Guide rods (25) are fixed to a first one (23) of the cross-members and slidably engaged in the second member (16) thereby to resist relative rotation of the members. Mounted on the guide rods (25) is a rotary motor (27) which is drivingly coupled by a crank drive (28, 29) and connecting rod (30) to the second cross-member (16). <IMAGE>

Description

SPECIFICATION Working element drive in material processing apparatus The present invention relates to material processing apparatus, such as a moulding or punching machine, and has particular reference to working element drive in such apparatus.

A drive device in the form of a toggle lever drive for a mould closing unit of an injection moulding machine is disclosed in DE-PS 11 16 386. In DE-AS 17 79 901 there is disclosed a drive device for the movement of the moulding table of a thermal moulding machine, the device being arranged in the moulding station. Hydraulic and pneumatic cylinders are used for drive of the toggle levers. Inexpensive pneumatic cylinders have proved suitable in thermal moulding machines and packaging machines. For many years such toggle lever drives including pneumatic cylinders have been incorporated in plastics material deforming and packaging machines.Such a drive is designated in the following for the sake of simplicity as a selfsupporting toggle lever drive and has the advantages of a high closing force, no lateral loading of guides, a construction permitting the entire station, at which it is mounted, to be displaced relative to the machine frame, since it does not stand in connection with this, and a simple construction allowing economic manufacture.

This form of drive does, however, have certain disadvantages. For example, on opening, strong shocks occur in the lower end position and a braking of the masses disposed in full travel requires hydraulic shock absorbers, which at high cyclic rates would have to be large is size due to heating, which is expensive. A relatively high energy consumption is involved, since compressed air is used for both movements, although a movement due to its own weight could take place in one direction.

Moreover, the pneumatic movement entails a limitation of the maximum possible cyclic rate because of the maximum flow speed of the compressed air.

The course of movement is also dependent on fluctuating air pressure and thereby not constant.

This is disturbing particularly in the moulding station, since different deformation conditions are then present and have a negative influence on the uniformity of the product. In the case of punching stations, a high punching impact and thereby a high noise pressure level occurs. This is due to the fact that a lower air pressure is needed for the closing of the punching station than for the punching. This higher pressure builds up slowly after the closing of the punching station and the punchingout of moulded articles takes place suddenly thereafter. Such punching impacts can be eliminated only with an appreciable effort. Although the first to the fourth of the mentioned disadvantages could be influenced by the use of hydraulic cylinders, a hydraulic system with valves and cylinders is relatively expensive.In addition, it does not permit high cyclic rates, due to the relatively slow movements.

It would thus be desirable to avoid the aforesaid disadvantages, while retaining the previously stated advantages.

According to the present invention there is provided material processing apparatus comprising two relatively movable material processing elements co-operable to process material received therebetween and a respective displacing drive to displace either or each of the elements to produce relative movement of the elements, the or each drive comprising two cross-members relatively movable towards and away from each other, toggle lever means to translate said relative movement of the cross-members into displacement of the associated one of the elements, guide rods fixed to one of the cross-members and guided in the other cross-member to permit said relative movement of the members but to resist relative rotation thereof, and a motor mounted on the guide rods and drivingly coupled by a crank drive and connecting rod to said other cross-member.

In a preferred embodiment it is advantageous that the use of a motor, which actuates a closing toggle lever by way of a crank rocker, achieves a particularly soft arrival in the extended position of the toggle lever, since the crank drive moves into an extended position. On the opening of the material processing elements, a soft braking is provided on arrival at the end position, since the crank rocker now passes into a reversal position with a sinusoidal coiurse of movement. Through this course of movement by way of the crank rocker, a high closing force is achieved, which is constrainedly guided so that it does not cause an uncontrolled punching and thereby a high punching impact. Shocks during opening are thus avoided by the course of movement of the crank drive.

Through the arrangement of the motor on guide rods, which extend between the two cross-members, at which toggle lever pairs are arranged, the entire toggle lever drive is of simple construction and cheap to manufacture, so that there is little difference in terms of manufacturing price compared to a drive with a pneumatic cylinder but a significant energy saving is achieved, because an electrical motor uses only the energy it actually needs for opening and closing. Moreover, the closing position can be set exactly through simple displacement of the motor on the rods so that the toggle lever is always exactly straight in the closing position. The drive by way of motor offers a constantly repeating course of movement and the stroke speed and thereby the cyclic rate can be set through appropriate choice of the output rotational speed of the motor.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of first apparatus embodying the invention, the apparatus serving for deforming a band of thermoplastic plastics material; Figure 2 is a cross-sectional view of a moulding station of the apparatus of Figure 1; Figure 3 is a cross-sectional view of a punching station of the apparatus of Figure 1; Figure 4 is a schematic side view of second apparatus embodying the invention, the apparatus serving for deformation of a band of thermoplastic plastics material into packages; Figure 5 is a cross-sectional view of a transverse cutting station of the apparatus of Figure 4; Figure 6 is a partly sectioned side view of a toggle lever drive in the apparatus of Figure 1;; Figure 7 is a plan view of the toggle lever drive of Figure 6; and Figure 8 is a sectional view of a modification of part of the toggle lever drive.

Referring now to the drawings, there is shown in Figure 1 apparatus for the deformation of a band of thermoplastic plastics material, the apparatus comprising a frame 1, a roll receptacle 2, a cyclically driven transport 3, a heater 4, a moulding station 5 and a punching station 6. In the illustrated embodiment, two movable tables - a lower table 7 and an upper table 8 - are arranged for the reception of tool halves 9 and 10 in the moulding station 5. Containers 12 are shaped by means of differential pressure from a cyclically moved, heated film web 11 and are severed from the web 11 in the punching station 6. Whether two movable tables 7 and 8 are present, or only one movable table, in the moulding station 5 depends on the kind of the deformation and the structure of the part to be moulded.

The construction of the moulding station 5 is shown in, in particular Figure 2. The upper table 9 and lower table 10 are guided on two guide columns 13, which are rigidly mounted in two crossbridges 14 and 15. A respective self-supporting toggle lever drive, the construction of which is evident from Figures 6 and 7, is mounted between the cross bridge 15 and upper table 8 and between the crossbridge 14 and lower table 7.

Two short straps 18 are connected at an axis 20 to the lower table 7 and similar straps 17 are connected at an axis 19 to the crossbridge 14. The straps are also connected to a crossbeam 16 at an axis 53. At the axes 19 and 20, long straps 21 and 22 are also connected and these lead to a crossbeam 23, to which they are rotatably connected at spigots 24.

Two guide rods 25, which serve for the guidance of the crossbeam 16, are fastened to the crossbeam 23; rotation of the two crossbeams 16 and 23 is prevented in simple manner by this connection. Arranged at the rods 25 is an adjustable plate 26 on which a motor 27 is mounted. The motor 27 actuates the toggle lever drive by way of a crank drive consisting of crank 28 and crank pin 29, and pushrod 30 which at its remote end is rotatably connected to the crossbeam 16 at an axis 31. In closed setting, the straps 17, 18, 21 and 22 form a triangle, i.e. the straps 17 and 18 form a straight line.

The drive of the upper table 8 can take place in analogous manner by a toggle lever drive acting between the upper table 8 and the cross-bridge 15.

The punching station 6 (Figure 3) following the moulding station 5 is, for example, a steel strip punch with movable upper table 32. Guide columns 34 are fastened in a frame 31 with a rigid lower table 37 and are connected by a bridge 35. A steep strip punching tool 36 for punching-out of containers 12 is fastened to the upper table 32. The toggle lever drive is mounted in analogous manner between the upper table 32 and bridge 35. The punching station can also be designed for fallthrough cuts. An analogous movement of the lower table 37 can be provided.

Since the spacing between the moulding station 5 and punching station 6 is preferably settable according to the spacing of the containers 12, the punching station is constructed either to be drivable as an individual unit or else to be displaceably mounted on longitudinal guides in the moulding machine.

Apparatus for the deformation of a band of thermoplastic plastics material into packages is illustrated in Figures 4 and 5. This consists of a packaging station 38 and a longitudinal and transverse cutting station 39. The station 38 is composed of a frame 40, a heater 41, two clamping frames 42 and 43 and a vertically movable moulding table 44. Packaging bodies 46, which are arranged as multiple useful parts on a carton 45, are laid on the moulding table 44 and packaged with vacuum in a known manner by film. The deformed band of contiguous packings is cut longitudinally by a longitudinal cutter 47 in the downstream longitudinal and transverse cutting station 38. A transverse cutter 48 carries out different transverse cuts and, by means of a clamping device (not shown), takes over the transport of the deformed band.For this purpose, the entire transverse cutter 48 is displaceable by way of a chain drive 49 on guides 52.

The severed packages 51 lie on a transport belt 50.

A cross-sectional view of the transverse cutter 48 is shown in Figure 5. Vertical guide columns 55 run in a rigid crossbridge 54, which rests on the guides 52, and are connected above and below to carriers 56 and 57. A transverse cutting blade 58, which cooperates with a locally fixed lower blade 59, is fastened to the upper carrier 57. The toggle lever drive is mounted between the crossbridge 54 and the lower carrier 56 so that a stroke movement of the carrier 57 takes place by way of the guide columns 55. The parts of the toggle lever drive in Figure 5 are designated by the same reference numerals as the corresponding parts in Figures 6 and 7.

If the self-supporting toggle lever drive is incorporated in a punching station, then the motor 27 in operation runs through about one revolution and then stops. The exact end position in the opened setting usually does not matter.

It is different when the toggle lever drive is incorporated into a moulding station. Then, a rest period, during which the moulding of the parts to be manufactured takes place, occurs in the closed setting of the moulding tools. This means that the motor 27 must stop fairly exactly so that the end position (closed setting) is consistently the same.

The use of a braking motor as the motor 27 may then be advantageous. Additionally, as shown in Figure 8, a resilient element can be built into the pushrod in order to compensate for slight inaccuracies. In that case, the pushrod is divided into a rod 60 and a sleeve 61. A spring 62 provides the force transmission and serves for compensation for small tolerances.

Of course, other motorised drives with exact stopping points are also feasible.

Claims

1. Material processing apparatus comprising two relatively movable material processing elements co-operable to process material received therebetween and a respective displacing drive to displace either or each of the elements to produce relative movement of the elements, the or each drive comprising two cross-members relatively movable towards and away from each other, toggle lever means to translate said relative move ment of the cross-members into displacement of the associated one of the elements, guide rods fixed to one of the cross-members and guided in the other cross-member to permit said relative movement of the members but to resist relative rotation thereof, and a motor mounted on the guide rods and drivingly coupled by a crank drive and connecting rod to said other cross-member.

2. Apparatus as claimed in claim 1, wherein the motor is a braking motor.

3. Apparatus as claimed in either claim 1 or claim 2, wherein the connecting rod comprises a member variable in length against a resilient bias.

4. Apparatus as claimed in any one of the pre ceding claims, the apparatus being a moulding machine for moulding articles from thermoplastic plastics material.

5. Apparatus as claimed in any one of the pre ceding claims, the apparatus being a punching ma chine for cutting or impressing thermoplastic plastics material.

6. Apparatus substantially as hereinbefore de scribed with reference to Figures 1 to 3, 6 and 7 of the accompanying drawings.

7. Apparatus substantially as hereinbefore de scribed with reference to Figures 4 and 5 of the ac companying drawings.

8. Apparatus as claimed in either claim 6 or claim 7 and modified substantially as hereinbefore described with reference to Figure 8 of the accom panying drawings.