GB2183589A - An overload protection device - Google Patents

Abstract

A multicable conveyor system, ie an elevator, has each cable connected to the cage by a harness which includes a hydraulic piston and cylinder. Each cylinder 8 has a respective accumulator 19 connected thereto by way of a connection unit 23. Each cable is tensioned by the pressure of the cylinder 8 with the piston rod 12 extended. The piston rod 12 moves only when the pull on the cable is greater than the pressure. The piston, cylinder and accumulator act as an overload protection unit and are interchangeably mounted in the harness 1 through the agency of an abutment plate 20 and a clamping lever 21. <IMAGE>

Description

SPECIFICATION An overload protection device The invention relates to an overload protection device, more particularlyforthe cables of multicable conveyors, as set out in the preamble of claim 1.

PamphetAS 100-157 E issued bytheASEA company of Vasteras, Sweden, makes it known to include hydraulically operated cylinders in intermediate harnesses embodied by inner links and outer links guided positively on one another. All the cylinders are so connected by hydraulic lines asto communicate with one another and are adjustable by means of a portable hydraulic pump. After adjustmentthe pump is disconnected from the hydraulic system.

A disadvantage of the known construction is that, since the cylinders are in permanent communication with one another, even minor alterations in the pulls on the cables caused, for example, by alterations in cable length or by different cable-run diameters of the driving pulleys, cause displacement ofthe pistons and piston rods relatively to the cylinder bodies. Consequently, the cylinders and the rest of the hydraulic system experience continuous wear with the attendant risk of leakages. What makes this particularly clear is the consideration that, depending on depth, for example, differences of only a few tenths of millimetres between the cable-run diameters ofthe pulleys can produce differences in height near the intermediate harnesses of from 50to 100 mm.

Another disadvantage ofthe known system is that in the event of damageto the intercommunicating hydraulic system with substantial losses of hydraulic fluid, the whole system may fail, with serious effects for proper operation of a multicable conveyor.

In addition to such a permanently operative compensating system, it is known, for example, from the periodical "Glückauf" of 22.10.1960, page 1411, Figures 53 and 54, to produce changes in the length of intermediate harnesses by means of hydraulic cylinders without location of the cage on full bottom-run load and without the cable being freed from load and secured; however, afterthe length has been altered, the operating position is secured mechanically by fork-like fittings.

It is the object of the invention so to improve the overload protection device described in the preamble of claim 1 astoreducewearsubstantially and virtually obviate the risk of leakages.

The features set out in the operative part of claim 1 are intended to solve this problem.

The invention associates with each harness a separate closed fluid circuit having a power source for continuous variation of the length of the harness in response to external pulls (loads). An overload protection device of this nature is operative as a closed unit devoid of any electrical or hydraulic or pneumatic connection. Any damage to a unit does not effect the units associated with the other harnesses. Sincethe response pressure ofthe units can be adjusted to any desired limit load, the units perform fewer movements than the known intercommunicating hydraulic systems, more particularly in response to changing loads caused by reversal of the direction of conveyance.

Consequently, the fluid circuits according to the invention and the cylinders and accumulators forming part of such circuitsaresubjectto much less wearthan the prior art systems. The invention greatly reduces the risk of leakages. Each fluid circuit can be hydraulically or pneumatically operated.

The features of claim 2 provide additional visual monitoring of cable elongation, while the coloured marking panels according to claim 3 make even more clearly visible that the maximum compensating length of the harness has been reached.

Thefeatures of claim 4 enable the cylinder and accumulatorto be demounted and reassembled readily; the cylinder is releasably secured to one side ofthe abutment plate and the accumulatortogether with the connection unit to the other side of the abutment plate. When such a unit is assembled in an intermediate harness, the abutment plate locates the operative position of the cylinder when it abuts an outer link of the harness. The locating device, such as a rotatable lever, disposed on the other side ofthe cylinder body co-operates with the abutment plate to prevent the unit from dropping out of the harness.

The features of claim 5 provide substantially independent adjustment ofthe cylinder in the harness. The socket-like mountings can take the form of spherical plates associated on the one hand with the inner link and on the other hand with the outer links.

Thefeaturesofclaim 6 fu rther enhance the overload protection for the cables. The safety valve can be more particularly a pressure-limiting valve which is readily adjustable to the maximum permissible load.

The stop valve according to claim 7 serves to interruptthe hydraulic communication between the cylinder and the accumulator as required.

The features of claim 8 provide a convenient association between the safety valve and the stop valve and facilitate the assembly and demounting of a compensating unit.

When for rapid and reliable detection of differences in cable lengths and differences in cable-run diameters the compensating units according to the invention are combined with units comprising rockers or bent levers, the number of compensating units can be reduced correspondingly in accordance with the design of the detecting facilities.

The invention will be described in greater detail hereinafterwith reference to an embodiment illustrated in the drawings wherein: Figure 1 is an elevation ofthe intermediate harnesses of a six-cable conveyor; Figure2 is another view in elevation of an intermediate harness ofthe conveyor of Figure 1; Figure 3 is a vertical section on the line Ill-Ill of Figure 2; Figure4is an elevation of a length-compensating unit introducible into an intermediate harness, and Figure 5shows the circuit diagram ofthe compensating unit of Figure 4; Referring to Figure 1, a six-cable conveyor has intermediate harnesses 1-1 e. The cables apply to the harnesses 1-1 e pulls S-SS and the harnesses have connections V-V5 to a cage suspension (not shown in greater detail).

As can be seen in the case ofthe harness 1 shown in Figures 2 and 3, each harness 1-le has an innerlink 2 and two outer links 3,4. The links 2 -4are positively guided on one another in a manner not shown in greater detail.

Each link2-4isformedwith recesses 5 -7 and receives a hydraulically actuated cylinder 8. The same bears byway of its body 9 on a plate 10 having a socket-like mounting 11 secured to the inner link2.

A piston rod 12 also bears on a plate 13 having a socket-like mounting 14, the plate 13 being secured to a web 15 interconnecting the two outers link 3,4.

Consequently, when the cylinder 8 is energized, the abutment positions 16, of the inner link 2 and outer links 3,4 are moved apartfrom one another.

As can be gathered from a consideration of Figures 1 - 4together, the cylinder8 is releasably secured to one side of an abutment plate 20 and an accumulator 19 which communicates with the cylinder 8 by way of a line 18 is releasably secured to the other side ofthe plate 20. Atwo-armed clamping lever 21 is rotatably mounted on that side of the cylinder body 9 which is diametrically opposite the plate 20.

When the cylinder 8 is introduced into the harness 1,the plate 20 abutstheouter link3 and thus locates the cylinder8 in its operative position. Afterthe clamping lever 21 has been turned from the position shown in Figure 4 into engagement with an abutment 22 - i.e., into the position shown in Figures 1-3-the lever 21 abuts the other outer link4, sothat the cylinder8 is secured against dropping out ofthe harness 1.

As can also be gathered from Figures3 - 5, a connection unit 23 is provided in the line 18 between the cylinder 8 and the accumulator 19. A manually adjustable pressure-limiting valve 24, a pressure gauge 25 associated therewith and a manually operated stop valve 26 form part of the unit 23. The pressure-limiting valve 24 has a control lever 27 and the stop valve 26 has a control lever28.

In the normal operating position the stop valve 26 is open, as shown in Figure 5. Movement of the stop valve 26to its other operative position cuts off communication between the cylinder 8 and the accumulator 19.

The maximum load on the harness 1 is determined bythe pressure with the piston rod 12 extended and the accumulator 19 is secured by adjustment ofthe pressure-limiting valve 24.

As Figures 1 and 2 show, a displacement scale 29 is provided on the outer link 4 of the harnesses 1 - 1 e.

The scale 29 co-operates with a pointer 30 secured to the cylinder body 9. The scale 29 can also have coloured marking panels 31 - 33 giving a visual indication ofcabieelongation.

Claims (10)

1. An overload protection device, more particularly for the cables of multicable conveyors, which has fluid-actuated cylinders operative between links of intermediate harnesses, such links being movable relatively to one another, characterised in that an accumulator (19) operative as spring element and forming part of a fluid circuit (8,18,19) independent of the other cylinders (8) is associated with each cylinder(8).

2. A device according to claim 1, characterised in that a displacement scale (29) is provided on a harness link (4) operated by the piston rod (12) ofthe cylinder(8) and a pointer (30) movable along the scale (29) is secured to the cylinder body (9).

3. A device according to claim 2, characterised in that the displacement scale (29) has coloured marking panels (31 - 33).

4. A device according to claim 1, characterised in thatthe cylinder (8) and the accumulator(19) are secured to an abutment plate (20) and a locating device (21) is provided on the cylinder (8).

5. A device according to claim 1 or4, characterised in that the cylinder(9) is clamped interchangeably between socket-like mountings (11, 14) provided in the links (2-4).

6. A device according to claim 1, characterised in that a safety valve (24) is connected to the fluid circuit (8,18,19).

7. Adeviceaccordingtoclaiml or6, characterised in that a stop valve (26) is provided in the fluid circuit (8,18,19).

8. A device according to claim 6 or 7, characterised in that the safety valve (24) and the stop valve (26) form part of a connection unit (23) disposed between the cylinder (8) and the accumulator (19).

9. An overload protection device, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

10. Any novelfeature orcombination offeatures described herein.