US3834524A

US3834524A - Conductor loops for ascertaining damage in steel cable reinforced conveyer belts

Info

Publication number: US3834524A
Application number: US00258426A
Authority: US
Inventors: W Ratz; W Laval
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1971-07-21
Filing date: 1972-05-31
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: BE784456A; ATA431272A; CA952210A; DE2136347B2; DE2136347C3; DE2136347A1; CH541493A; FR2146366B1; FR2146366A1; JPS5233869B1; IT959089B; GB1338530A; AT329436B

Abstract

An arrangement for ascertaining damage in a steel cable reinforced conveyer belt in which a plurality of conductor loops are arranged spaced from each other along the conveyer belt and in which each of the conductor loops is formed by a pair of conductor bridges and portion of two different cables of the belt between opposite ends of the bridges which are respectively electrically and mechanically connected to these cables. Damage of any of these bridges will result in signals in a receiver device outside the belt and electromagnetically coupled with the loops, when the damaged loop is located within the effective range of a transmitter and a receiver device.

Description

United States Patent Ratz et al.

CONDUCTOR LOOPS FOR ASCERTAINING DAMAGEIN STEEL CABLE REINFORCED CONVEYER BELTS Inventors: Walter Ratz, Gelsenkirchen; Willy Laval, Saarbrucken, both of Germany Bergwerlsverband GmbH, Essen, Germany Filed: May 31, 1972 Appl. No.1 258,426

Assignee:

Foreign Application Priority Data July 21, 1971 Germany 2136347 References Cited UNITED STATES PATENTS 8/1971 Halback l98/232 Primary Examiner-Richard E. Aegerter Attorney, Agent, or FirmMichael S. Striker ABSTRACT An arrangement for ascertaining damage in a steel cable reinforced conveyer belt in which a plurality of conductor loops are arranged spaced from each other along the conveyer belt and in which each of the conductor loops is formed by a pair of conductor bridges and portion of two different cables of the belt between opposite ends of the bridges which are respectively electrically and mechanically connected to these cables. Damage of any of these bridges will result in signals in a receiver device outside the belt and electromagnetically coupled with the loops, when the damaged loop is located within the effective range of a transmitter and a receiver device.

9 Claims, 9 Drawing Figures 4 5 2 6 3 l -l---- IP [2 /'-1 2b 20 2b R T CONDUCTOR LOOPS FOR ASCERTAINING DAMAGE IN STEEL CABLE REINFORCED CONVEYER BELTS BACKGROUND OF THE INVENTION In conveyer installations the danger always exists that sharp edged bodies, for instance stone or metal parts, are wedged in at the inlet or transfer portions of the conveyer so that the latter is longitudinally torn by these sharp edged bodies. Such slits may reach, especially if the conveyer belts are operated at high speed, in a short time the length of 100 meters or more.

Many suggestions have already been made to instantaneously ascertain the occurrences of such slits so that the damaged conveyer belt may be instantaneously stopped to prevent extensive damage of the same. Some of the known suggestions are based on the principle to transmit high frequency radiation from one or a plurality of stationary transmitters mounted adjacent the conveyer belt to conductor loops mounted on or incorporated into the upper cover layer of the belt and which produce signals in receiving devices likewise stationarily arranged adjacent to the belt, which signals are varied if one of the conductor loops is damaged so that damage in the belt can be ascertained when the damaged loop becomes located within the effective range of a transmitter and receiver device.

The conductor loops in arrangements known in the art essentially comprise endless wire loops which, of any desired configuration, such a circle, rectangle or similar configuration, are spaced from each other built in the conveyer belt so that they substantially cover the whole width of the belt. Such conductor loops may be built into the conveyer belt during manufacturing of the same or be subsequently attached thereto at selected distances of about 25 to 50 meters from each other. For expensive or fast moving conveyer belts it is preferred to arrange the consecutive loops closer, for instance to meters from each other. In this case it is also advisable to install a greater number of transmitters and receiving devices along the conveyer belt.

inserted therein built into the conveyer belt. Instead of spirally formed wires it is also possible to use wires or metal bands which are wound or braided about a core of elastic material. Thereby it is possible to use two or more wires or bands, as in the manufacture of electrical cables, which are wound about the elastic core. The thus formed conductor is then likewise imbedded in tubes of elastic material. The incorporation of such conductor loops into or attachment to conveyer belts is however difi'icult and expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide conductor loops in conveyer belts for the abovementioned purpose which can be manufactured in a simpler and less expensive manner than conductor loops known in the art and which nevertheless will perfectly serve the purpose for which they are to be used.

Applicant has ascertained that in conveyer belts in which longitudinal extending steel cables are incorporated it is possible to produce conductor loops suitable for the above-mentioned purpose by connecting two transversely spaced cables by means of two conductor bridges with each other.

Each of the conductor loops according to the present invention is therefore constituted by a pair of conductor bridges extending transverse to the elongation of the conveyer belt between two different transversely spaced steel cables of the belt which are mechanically and electrically connected at opposite ends to the two steel cables, and the portion of the cables between the connected ends of the conductor bridges. A precondition for the proper functioning of the conductor loops is that at least one of the conductor bridges of each loop is insulated from the steel cables it transverses and only electrically connected at the ends thereof to the respective two steel cables, and that adjacent conductor loops are spaced a certain minimum distance in longitudinal direction of the belt from each other. If during extended use of the conveyer belt the insulation 'of one of the conductor bridges should be damaged, the loop will still function. The proper function will be impaired only when both bridges make contact with one and the same cable they traverse. If the opposite ends of the pair of conductor bridges which form a single conductor loop are respectively connected to the same steel cables, then the minimum distance between adjacent loops should be about 8 meters, whereas when the opposite ends of the pair of conductor bridges forming each loop are respectively connected to different steel cables, then the minimum distance between adjacent conductor loops may be reduced to about 3 or 4 meters.

A distance of about 10 to centimeters between the pair of conductor bridges forming an individual conductor loop has been proven suitable, whereby the conductor bridges need not necessarily extend parallel to each other. While generally the conductor loops will have a substantially rectangular configuration, it is also possible in order to reduce the connecting points between the conductor bridges and the steel cables to form each conductor loop in the form of a triangle. The conductor bridges may be connected at the opposite ends thereof by clamping members or by plaiting or entwining to the respective steel cables of the conveyer belt. Evidently, it is also possible to connect the ends of the conductor bridges by soldering or welding to the steel cables.

If the steel cables of the conveyer belt are imbedded in rubber or similar insulating material, then it is possible to use for the conductor bridges bare wires, or wires insulated in the manner as above described. If the con ductor loops have to be provided in the conveyer belts after the latter have been finished, it is sufficient to cut into the upper cover layer of the belt appropriate grooves into which the conductor bridges are then imbedded. Care has to be taken that the blank ends of the conductor bridges and the blank portions of the steel cables to which the ends of the conductor bridges have to be connected, are again properly insulated after the connection has been made, for instance by a mass of rubber or similar insulating material, to protect the connection against mechanical damage or corrosion.

To avoid the danger of loosening of the connection between the cuts of the conductor bridges and the steel cables to which they are connected, it is advantageous to surround the connection with conductive rubber. In this case it is sufficient to loosely wrap the free end of the wire of the conductor bridge around the steel cable and to surround the connection with conductive rubber so that the mechanical and electrical connection is mainly established by the conductive rubber. Of course, it is also possible to make the connection by clamping or by braiding the wire with the steel cable or by soldering or welding or by casting around with a metal.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial schematic plan view of a conveyer belt provided with conductor loops and FIG. 1 schematically indicates also a transmitter and a receiving device adjacent the conveyer belt, while for reason of clarification the upper cover layer of the conveyer belt is removed in FIG. 1 and in the other Figures;

FIG. 2 is a partial plan view of a conveyer belt showing a modified conductor loop arrangement;

FIG. 3 is a partial plan view of a conveyer belt showing a further modification of a conductor loop;

FIG. 4 is a partial plan view of a conveyer belt showing an additional modification of a conductor loop;

FIG. 5 is a partial plan view of a conveyer belt showing another modification of a conductor loop;

FIG. 6 is a partial plan view of a conveyer belt showing yet another modification of a conductor loop;

FIG. 7 is a partial enlarged plan view showing the connection of one end of a conductor bridge to one of the steel cables of the conveyer belt;

FIG. 8 is a view similar to FIG. 7 and showing a different kind of connection; and

FIG. 9 is a view similar to FIG. 8 and showing another kind of connection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 partially illustrates in a schematic manner a conveyer belt according to the present invention which is provided with a plurality of conductor loops, only two of which L and L are shown in this Figure. The conveyer belt 1 comprises a plurality of steel cables only the outermost of which are referred to with the reference numerals 3-6. These cables extend substantially parallel to each other in longitudinal direction of the conveyer belt and are imbedded in a mass of insulating material, such as rubber or the like, and for clarification reason the upper cover layer of the belt is removed in FIG. 1. Each of the conductor loops L and L comprises a pair of conductor bridges 2 which are respectively connected at the right ends thereof, as viewed in FIG. 1, at

points

2 and 2a to the cable 3 adjacent to the right edge of the conveyer belt 1, whereas the left ends of the conductor bridges are connected at the points 212 and 20 to the cable 4 adjacent to the left edge of the conveyer belt, and the portions of the

cables

3 and 4 respectively extending between the

points

2 and 2a and the

points

2b and 2c. As shown in FIG. 1, the conductor bridges forming the adjacent conductor loop L are connected at the opposite ends respectively to the

same cables

3 and 4. In such an arrangement the minimum distance d between adjacent conductor loops has to be 8 meters. It is mentioned that FIG. 1 is not drawn to scale since the distance d, in actuality is much greater than the width of the conveyer belt. In FIG. 1 the conductor bridges 2 are shown as extending substantially parallel to each other and substantially normal to the longitudinal direction of the cables and the distance between the two bridges at each loop is preferably between 10 to centimeters.

FIG. 1 also schematically indicates a transmitter T located adjacent the conveyer belt for transmitting high frequency radiation to the conductor loops and a likewise stationary receiver R adjacent the conveyer belt adapted to receive in a known manner signals from the conductor loops, which signals are modified whenever any of the conductor loops is damaged due to tearing of the conveyer belt so that the conveyer belt may be instantly stopped if such damage occurs to prevent increase of such damage. Stopping of the conveyer may be initiated by an operator observing the modified signal or the modified signal may act on an appropriate electronic device which in turn stops the conveyer belt drive.

The construction and operation of the transmitter T and receiver R do not form part of the present invention and these devices are well-known in the art and need, therefore, no further explanation.

FIG. 2 shows a slight modification of the arrangement of the conductor loop. The conductor loop L shown in FIG. 2, is identical in construction and arrangement with the conductor loop L shown in FIG. 1, however, the adjacent conductor loop L differs slightly from the conductor loop L in that the two conductor bridges 2' are connected at their right ends, as viewed in FIG. 2, not to the cable 3, but at the points 2d and 2e to the cable 6 adjacent thereto, whereas the left ends of the two conductor bridges are connected at the points 2g and 2f to the cable 5 adjacent to the cable 4. In this construction in which the opposite ends of conductor bridges forming adjacent conductor loops are respectively connected to different cables, the distance d between adjacent loops may be reduced as compared to the distance (1, shown in FIG. 1, and the minimum distance in the arrangement shown in FIG. 2 may be between 3 and 4 meters so that damage occurring by longitudinal slits in the conveyer belt may be ascertained already in extremely short time. While the conductor loop L shown in FIG. 2 has the disadvantage that damage occurring in the marginal portions of the conveyer belt outside of the

cable

5 and 6 will not be indicated, such disadvantage seems negligible since longitudinal tearing in the outer marginal portion of the belt occurs very rarely.

FIG. 3 illustrates a modified arrangement in which two shorter conductor loops L and L are provided which are transversely offset with respect to each other to guard especially the center portion of the conveyer belt in which damage is most likely to occur.

FIG. 4 illustrates another modification of a conductor loop. The conductor loop L shown in FIG. 4,

which is of substantially triangular configuration comprises two conductor bridges 2" which extend inclined under an angle to each other and their left ends are connected at a single point 2k to the cable 4, whereas the right ends thereof are respectively connected at the

points

2h and 2i to the cable 3 so that the conductor loop 1..., comprises only the two conductor bridges 2" and the portion of the cable 3 extending between the

points

2h and 2i.

FIG. 5 shows a further modified conductor loop L in which the conductor bridges 2" are offset between the opposite ends thereof so that each of the conductor bridges has a zig-zag configuration. The two conductor bridges are connected at the right ends thereof, as viewed in FIG. 5, respectively at the

points

21 and 2m to the cable 3, whereas their offset left ends are connected at the points and 2p at the cable 4.

FIG. 6 shows a still further modification of a conductor loop L which is constructed to facilitate repair of the same when one of the conductor bridges is damaged. One of the conductor bridges 2"" is connected at opposite ends at the points 2q and Zr to the

steel cables

3 and 4, whereas the other conductor bridge comprises two transverse portions offset in longitudinal direction of the conveyer belt, one of which is connected at the

points

2s and 2t to the

steel cables

4 and 7 and the other of which is connected at the points 2n and 2v to the

cables

7 and 3, and a connecting portion between the points 22 and 214 formed by the cable 7. If only one of the transverse portion is destroyed it can be easily replaced.

' FIG. 7 illustrates at an enlarged scale the connection of the blank end of one of the conductor bridges 2 to a cable, for instance the cable 3 by means of a clamping member 7 of any known construction, whereas FIG. 8 schematically illustrates another connection in which the blank end of the conductor bridge 2 is connected for instance to the cable 3 by a spiral or braiding arrangement 8. As mentioned before, at least one of the conductor bridges has to be insulated from the cables it traverses and the blank end portions of the conductor bridges as well as the blank portions of the cable to which they are connected have to be properly insulated again after the connection has been made.

FIG. 9 illustrates a connection in which the blank end 8 of the conductor bridge 2 wound about the cable 3 is surrounded with a mass of conducting rubber 10.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of conductor loops differing from the types described above.

While the invention has been illustrated and described as embodied in conductor loops on conveyer belts for ascertaining damage in the latter, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In an arrangement for ascertaining damage in a reinforced conveyor belt, a combination comprising a conveyor belt having longitudinally extending and transversely spaced steel cables embedded in insulating material; a plurality of closed conductor loops arranged spaced from each other in longitudinal direction of said belt, each of said conductor loops comprising a pair of conductor bridges extending transverse to the elongation of said conveyor belt and spaced from each other in the longitudinal direction of said belt between two transversely spaced steel cables and being at opposite ends mechanically and electrically connected to said transversely spaced steel cables to form with portions of said cables between said connected ends said closed conductor loops; and stationary transmitter and receiver means adjacent said belts and operative to provide a signal upon destruction of any of said conductor loops.

2. A combination as defined in claim 1, wherein said cables to which the ends of said conductor bridges are connected are located in the region of opposite longitudinal edges of said conveyer belt.

3. A combination as defined in claim 2, wherein the conductor bridges of adjacent loops are connected at opposite ends respectively to the same cables and wherein the minimum distance between the adjacent loops is 8 meter.

4. A combination as defined in claim 2, wherein the conductor bridges of one of a pair of adjacent loops are connected at opposite ends respectively to different cables than the conductor bridges of the other of the pair of adjacent loops, and wherein the minimum distance between said adjacent loops is 3-4 meters.

5. A combination as defined in claim 1, wherein the conductor bridges of each loop are spaced about 10-100 centimeters from each other.

6. A combination as defined in claim 5, wherein the conductor bridges of each loop extends substantially parallel to each other.

7. A combination as defined in claim 6, wherein the conductor bridges of each loop extend substantially normal to the direction of elongation of the conveyor belt.

8. A combination as defined in claim 1, wherein the conductor bridges of each loop extend inclined at an angle with respect to each other.

9. A combination as defined in claim 8, wherein the conductor bridges of each loop are connected at one of the ends thereof at the same point to one of the said two cables.