GB2062760A

GB2062760A - Apparatus for the Discontinuous Feed of a Line of Pallets for the Production of Concrete Roofing Tiles

Info

Publication number: GB2062760A
Application number: GB8016806A
Authority: GB
Original assignee: Redland Roof Tiles Ltd
Current assignee: Redland Roof Tiles Ltd
Priority date: 1979-11-10
Filing date: 1980-05-21
Publication date: 1981-05-28
Also published as: IT1127776B; DE2945553A1; DK537079A; CH642588A5; AT373536B; IT7928453A0; ATA805379A

Abstract

Apparatus for the discontinuous feed of a line of pallets (1) through the concrete supply station of a roofing tile production line comprises a double acting ram (7, 8, 9), the piston rod (9) of which is connected to a pawl (11) which engages the pallets to move them. The cylinder (7) has a series of supply holes (18, 20) adjacent each of its ends which are gradually covered and uncovered by movement of the piston (8) so that pressure fluid supplied to one end of the cylinder with accelerate the piston at the start of its stroke and release of fluid from the other end of the cylinder will decelerate the piston at the other end of its stroke. <IMAGE>

Description

SPECIFICATION Apparatus for the Discontinuous Feed of a Line of Pallets for the Production of Concrete Roofing Tiles The invention concerns apparatus for the discontinuous feed of a line of pallets for the production of concrete roofing tiles, by means of a hydraulic cylinder drive which propels the line of pallets forward step by step, with a double-acting piston and a one-sided piston rod, the cylinder drive starting up slowly, with partial throttle, at the beginning of the propulsion.

in contrast to continuously operating devices (for example in accordance with German Patent 1 6 83 785), discontinuously operating devices of the type mentioned above have the advantage that, while they are at a standstill, the cutting processes which are necessary to separate individual concrete roofing tiles from a line of pallets and to produce additional and complicated cuts, such as on the side cloak for verge tiles or openings in ventilating tiles, can be carried out by means of stationary cutting devices, while in the case of continuous drive the cutting devices must be exactly co-ordinated with the moving line of pallets.On the other hand, discontinuously operating devices have the disadvantage that, because of the standstill periods, either the speed of production is reduced or, if the standstill periods are to be compensated for, it is necessary to have relatively high maximum speeds, which have an adverse effect on the quality of the goods to be produced. In the case of continous drive, the difficulties involved in the exact co-ordination of the cutting devices for complicated cuts are particularly great, because significantly longer times are needed for these than for standard cuts, such as are needed to separate each tile from the pallet line, these times being approximately 1/10 to 2/10 sec. against 5/100 sec. for a standard cut; in such cases the discontinuous mode of operation is preferred.Attempts have been made to counter the especially undesirable relatively great accelerations involved by using a hydraulic cylinder drive (for example as shown in German Patent 2,823,834) which starts up slowly, with partial throttle, at the beginning of the propulsion.

Such throttle devices are, however, relatively expensive and allow of no direction-dependent control of the rates of acceleration or deceleration in adapting one and the same plant to the production of different profiles of concrete roofing tiles.

The invention provides apparatus for the discontinuous feed of a line of pallets for the production of concrete roofing tiles by means of a hydraulic piston and cylinder drive, which propels the line of pallets forwards step by step, and comprises a double-acting piston and a one-sided piston rod, in which the hydraulic cylinder has adjacent each end control orifice means arranged to be gradually opened or closed by movement of the piston and a source of pressure is provided which supplies a pressure medium at a pressure which remains substantially the same, means being provided to connect the supply of pressure medium to the end of the hydraulic cylinder remote from the piston rod during the propulsion stroke of the piston.

A discontinuous drive such as described above may at low cost and with relatively low rates of acceleration and deceleration, ailow a constant speed over a relatively large part of the propulsion distance, such as will make it possible to fill the concrete into the pallets at a steady rate and will also give standstill periods such that, on the one hand a high production speed can still be achieved, but on the other hand even complicated cutting processes can be carried out with stationary cutting devices. There may also be the possibility of a simple adaptation for concrete roofing tiles of various dimensions.

With no additional expenditure on controls, this construction makes it possible, by simple selfregulation of the piston in the hydraulic cylinder, to obtain a moderate acceleration of the line of pallets up to a maximum propulsion speed which remains constant over the largest part of the propulsion distance. Next, the line of pallets is braked to a standstill with equally moderate deceleration. The return stroke takes place at a higher speed and higher rates of acceleration and deceleration, corresponding to the smaller effective piston surface when the piston is activated from the end facing the piston rod.To keep the rates of acceleration and deceleration constant, it is merely necessary, when a pressure medium of constant viscosity is used, to maintain a constant pressure is the hydraulic system, which can be done in a simple manner by using a so-called zero-stroke pump in the form of a vane pump with adjustable displacement volume and possibility of setting the maximum operating pressure.

The device can easily be adapted to variously dimensioned concrete roofing tiles, since adjoining a propulsion feed-slide connected to the piston rod there may be adjustable proximity for switching over a multi-directional control valve which regulates the supply of the pressure medium to the hydraulic cylinder.

A preferred embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which Figure 1 shows a schematic side view of a device for conveying a line of pallets in accordance with the invention together with a device for filling in the concrete and subsequent cutting devices, Figure 2 shows an enlarged detail, partly in section, of the device for conveying a line of pallets as in Figure 1, Figure 3 shows a hydraulic circuit diagram for the device of Figure 2, and Figure 4 shows a speed-time curve for the device by way of explanation to elucidate the invention.

Pallets 1 forming a continuous line of pallets are conveyed (from right to left as viewed in Figure 1) on guide strips 2 by a belt (not shown in Figure 1) to a filling station comprising machine hopper box 3 with a spiked pack shaft 4, a compacting roller 5 and a slipper 6, by means of which concrete is fed into the pallets. The frictional forces occurring in the process are so great that the conveyor forces exerted by the belt are not adequate to transport the pallets through the filling station. For this purpose a separate propulsion drive is provided, comprising a hydraulic cylinder 7 with a double-acting piston 5 and one-side piston rod 9, on whose outer end a propulsion feed-slide 10, with a propulsion pawl 11, is fixed.This propulsion pawl engages each pallet 1 near the lower rear end (in the direction of propulsion) and engages at a place 12 at the beginning of a part of the guide strip 2 which is lowered.

The propulsion feed-slide 10 can slide along a feed-slide guide 13, and proximity swtiches 1 4a and 14b, for reversing the hydraulic cylinder 7, are fixed at the two ends of the feed-slide guide.

At the outlet end of the machine hopper box (concrete container) 3 is a stationary separating knife 1 5 to separate the individual concrete roofing tiles from the line of concrete which is until then carried along a continuous line on pallets 1; there is also another knife 1 6 to make cuts such as carried out on the side clock of verge tiles.

As shown in Figure 2, the hydraulic cylinder 7 has a pressure medium supply passage 17, leading to one end of the cylinder, and from this supply passage there branch off control holes 18 lying one behind the other in the direction in which the piston 8 moves; there is also a pressure medium return passage 19 which leads to the other end of the hydraulic cylinder and from which control holes 20 branch off in the same way.

On the propulsion feed-slide 10, the propulsion pawl 11 can, by means of a small swivel cylinder 22, swivel anti-clockwise on a swivel axis 21 in such a way that, on the return stroke of the propulsion feed-slide, the pawl can pass under the lower edge 23 of a pallet 1 which has meantime just run on to the lowered part of the guide track 2, as is shown in Figure 2 with broken lines.

As shown in Figure 3, the hydraulic passages 17 and 19 are connected to a multi-directional control valve 24, which can be reversed by means of the proximity switches 1 4a and 14b, of which the proximity switch 1 4b can be fixed parallel to the feed-slide guide 13 in a range as indicated in Figure 1 by the double-headed arrow, in order to adapt the device for pallets of different lengths.

From the multi-directional control valve 24, another hydraulic pipe 25 leads to a pump 26 with adjustable displacement volume and setting for maximum operating pressure, and driven by a motor 27. A second hydraulic pipe 28 leads from the multi-directional control valve 24 to a hydraulic reservoir 25.

The mode of operation of the drive is as follows: In the position of the propulsion feed-slide as shown in Figures 1 to 3, the feed-slide, by means of the proximity switch 14b, reverse the multidirectional control valve 24 so that pressure medium is fed by the pump 26 through the pipes 25 and 1 7 to the control holes 18, whereby with the movement of the piston 8, more and more control holes are uncovered and correspondingly more pressure medium is fed to the hydraulic cylinder 7, without this involving a fall in pressure, as the pump keeps the pressure in the hydraulic system constant. Maximum propulsion speed is determined by the maximum capacity of the pump.As soon as the piston 8 reaches the control holes 20 at the other end of the hydraulic cylinder, the piston, and with it the propulsion feed-slide, is retarded or braked correspondingly by automatic control as in the acceleration process. When the proximity switch 1 4a is reached, the multi-directional control valve 24 is again reversed, so that the pipes 19 and 25 on one side and 1 7 and 1 8 on the other side are now connected up, which causes the piston 8 with the propulsion feed-slide 10 to travel back at increased speed and increased rates of acceleration and deceleration, corresponding to the effective surface of the piston, which is now reduced by the cross-section of the piston-rod, as is shown in Figure 4, a speed-time diagram, by the unbroken curve 30. In comparison with this, the sine-shaped curve shown by the line of dashes demonstrates how, for example, the speed-time diagram appears in the case of a crank drive, which as hitherto been the type mainly used for drives of the sort concerned.

The form of construction described can, of course, be altered in various ways without departing from the scope of the invention as set out in the appended claims. For example, instead of the control holes arranged one behind the other at each end of the hydraulic cylinder, continuous control slots can be used.

Claims

1. Apparatus for the discontinuous feed of a line of pallets for the production of concrete roofing tiles by means of a hydraulic piston and - cylinder drive, which propels the line of pellets forwards step by step, and comprises a doubleacting piston and a one-sided piston rod, in which the hydraulic cylinder has adjacent each end control orifice means arranged to be gradually opened or closed by movement of the piston and a source of pressure is provided which supplies a pressure medium at a pressure which remains substantially the same, means being provided to connect the supply of pressure medium to the end of the hydraulic cylinder remote from the piston rod during the propulsion stroke of the piston.

2. Apparatus as claimed in claim 1 in which the control orifice means comprises a series of holes arranged to be covered and uncovered sequentially by movement of the piston.

3. Apparatus as claimed in claim 1 or claim 2 in which the connecting means comprises a multi-directional control valve and proximity switches for switching the valve, a propulsion feed-slide connected to the piston rod being arranged to operate, in use, the proximity switches.

4. Apparatus as claimed in claim 3 in which at least one of the proximity switches is adjustable.

5. Apparatus for the discontinuous feed of a line of pallets substantially as hereinbefore described with reference to and as shown in the accompanying drawings.