FOR MONITORING TRAWLS.

Background of the Invention.

The present invention relates to an apparatus for monitoring the angle setting of two wires. The apparatus is preferably intended for moni¬ toring the mutual angle setting of two trawl wires when monitoring trawls. However, the apparatus is generally useful for monitoring the mutual angle setting of two wires. Even though described herein with reference to trawl monitoring, it is understood that the subject in- vention may be useful in other applications.

During trawling the mutual angle setting of the trawl wires used to be checked in order to monitor the setting of the otter boards and the trawl. Thus, an inch rule was used to measure the distance between the trawl wires at two points spaced 1 meter apart. Comparison of the ex¬ tended wire length with the change in distance per meter extended trawl makes it possible to obtain an approximate measurement for the distance between the otter boards and to assess the setting of the appliance. Such measurements are to be carried out at regular inter- vals during trawling in order to ensure constantly correct positioning of the appliance. Aboard small vessels manual measurement is also used to estimate the amount of fish caught.

Such manual measurement is associated with several drawbacks. It is a dangerous task, especially in bad weather conditions, for the person to carry out the measurement as he has to lean over the rail of the ship. Moreover, said measurement involves a major risk for the person close to the wires. Owing to much stress in the wires there is a risk that they may part causing very serious personal injury. Furthermore, the measurement does not provide complete continuous control of the trawl setting. Continuous control may be of particular significance if a trawl is caught in the sea bottom in which event the trawl may easi¬ ly be damaged unless the vessel is stopped immediately. If the trawl is caught the distance between the trawl wires is reduced- So far it has been possible to exert continuous control only by a person keeping an uninterrupted watch on the setting of the trawl wires. This may not always be possible especially if the person keeping an eye on the wi¬ res is in the wheelhouse of the vessel. Moreover, a gradual change of angle settings, e.g. due to an otter board digging its way into the

sea bottom, may pass unnoticed until it is too late.

A system for measuring the distance between the otter boards is also known, viz. an acoustic system based on transmitters and receivers located on the otter boards and the vessel, respectively. Such acous¬ tic system provides measurement of the distance; it is very expensive, however, and thus constitutes an economically viable alternative only to a very limited number of vessels.

It is the object of the present invention to provide an apparatus for monitoring the angle setting of two wires, preferably for trawl moni¬ toring, wherein the above drawbacks are remedied and, furthermore, the manufacture of which is inexpensive thus presenting a useful apparatus for small and medium-size vessels.

This object is achieved with an apparatus according to the invention which is characterized in comprising two clamping members connecting the apparatus with each of the two wires, the one of said clamping members being secured so as to prevent displacement in the longitu- dinal direction of the associated wire, a rigid connection member which is located between and pivotally positioned on the clamping mem¬ bers, an electro-mechanical recording member connected to the secured clamping member and the connection member and constructed for mechani¬ cal recording of the angle setting of the connection member in rela- tion to the secured clamping member and for emitting an electric sig¬ nal depending on said angle setting, and a control unit comprising equipment for processing and display of the signal received. Monitor¬ ing of the angle setting of the two trawl wires makes it possible to assess the setting of the appliance. In use the apparatus is mounted on a crowfoot, i.e. immediately following the block running along a wire normally extended across the stern of the vessel. The crowfoot is fastened in this block and the ends thereof are provided with hooks or jaws for keeping the extended trawl wires in place. In the present specification the crowfoot is thus considered to constitute the first part of the trawl wires. In use, the apparatus is hence located on the part of the wires coming before the hooks or the jaws. As the one clamping member is secured so as to prevent displacement and the other clamping member may be displaced in the longitudinal direction of the associated wire, the rigid connection member is freely pivotable de-

pending on the angle setting of the trawl wires. Measurement of the connection member angle setting by the recording member permits emis¬ sion of a signal to the control unit which is, in turn, able to dis¬ play continuously the setting of the trawl wires. The use of different appliances is furthermore facilitated, knowing in advance the reading of the individiual appliance on the control unit. In use the control unit may advantageously constitute a separate unit and is preferably located in the wheelhouse of the vessel thus allowing for convenient continuous reading. Thereby it is rendered possible to exert simple, easy and continuous control of the trawl wire setting and moreover, the above apparatus in the embodiments appearing from the independent claims may be manufactured from simple as well as inexpensive elements.

The characteristics of claim 2 afford a high degree of operational safety for the apparatus as the recording member and optionally addi¬ tional sensitive equipment is provided in the form of a removable housing. During times of non-use the housing may thus be be disconnec¬ ted from the clamping member that remains connected to the trawl wires often subjected to rough handling on board the vessel.

It is noted that the term "wires" as used herein comprises any flexi¬ ble pulling member and therefore the term may comprise e.g. chains.

Description of the Drawings. The invention will now be described in further detail with reference to the accompanying drawings, wherein

Figure 1 is a sce atic view of the apparatus mounted on a stern traw¬ ler, Figure 2 is a partial side view of sections of the apparatus,

Figure 3 is a partial side view of the apparatus mounted on trawl wires, Figure 4 is a partial view illustrating the one clamping member and a section of the connection member mounted thereon, and Figure 5 is a partial view of the second clamping member and the con¬ nection member mounted thereon.

Figure 1 shows an apparatus 1 according to the invention used for mo¬ nitoring trawl wires 2 aboard a stern trawler. According to known

methods the trawl wires 2 are secured on a block 4 by jaws 3 and two trawl wires 2'. The block 4 is connected to a cross beam 6 located on the trawler stern by a wire 5. The cross beam 6 is provided with pul¬ leys 7 for the running out of the trawl wires 2 which are without load until they reach the jaws 3. The apparatus 1 comprises two clamping members 8,9 (vide also Figures 4 and 5), a rigid connection member 10, an electro-mechanical recording member 11, and a control unit 12.

Figure 2 illustrates the recording member 11 provided in a housing 13 connected to two square pipes 15 by means of two telescopic square pipes 14. The square pipes 15 are securely fastened to the clamping member 8. The housing 13 is provided with a cover 16 bolted to the housing 13 (at 17). Inside the housing the recording member 11 is pro¬ vided in the form of a rotary potentiometer, the operating shaft 18 of which being connected to an arm 19 intended for mesh with a recess 20 in the connection member 10 in order for it to follow the angle turn of the connection member. When the house 13 is mounted on the clamping member 8, the telescopic sliding of the pipes 14 and 15 causes the arm 19 to be received in the recess 20. The housing is subsequently secu- red by a safety split 21 which is inserted into aligned holes in the telescopic square pipes. The recording member 11 inside the housing 13 is connected to the control unit 12 by a cable 36. It further appears from Figure 2 that the operating shaft 18 is provided with two radial protrusions 22 intended for co-operation with a protrusion 23 on the housing which protrusion 23 is located between the two protrusions 22 in order to limit the angular motion of the operating shaft 18. Thus the rotary potentiometer escapes damage resulting from rotation, should the mutual setting of the wires cause an unacceptably high de¬ gree of angular motion. The housing 13 is moreover provided with a handle 24 for easy removal of the housing containing the relatively sensitive recording member 11.

Figure 3 shows the housing 13 mounted on the clamping member 8. The clamping member 8 is constituted by two profiles 25,26 which are fas- tened to each other with bolts 27 in order to form a longitudinally extending transfer channel for the wire 2'. Hence the clamping member is freely pivotable around the wire. Figure 4 shows that clamp rings 28 are placed at both ends of the clamping member in order to prevent movement of the clamping member in the longitudinal direction of the

wire. Moreover, it will appear that the connection member is consti¬ tuted by a square pipe profile which is pivotably mounted (at 29) on the clamping member and provided with the upwardly opening recess 20 for reception of the arm 19. The connection member pipe profile is moreover provided with a recess 30 for mesh with the radial protru¬ sions 22.

It will appear from figure 5 that the clamping member 9 is constituted by an eyebolt 31 and two nuts 32 mounted thereon and bolted so as to allow free rotation of the connection member 10 in relation to the eyebolt 31. It is essential that both clamping members 8,9 are freely rotatable around the wires, as the wires may intersect during the turning or pitching of the trawler. However, the clamping members be¬ ing freely rotatable, the apparatus of the invention simply rotates around its own longitudinal axis thus avoiding damage.

When the apparatus is to be assembled for use the housing is placed on the secured clamping member 8 and the control unit is preferably loca¬ ted in the wheelhouse of the vessel. The control unit 12 is construc- ted so as to process the signal emitted from the rotary potentiometer and to display the signal received. Thus, the control unit comprises a display 33, a transformer 34 for adjustment of various sensitivities, and a switch 35. During trawling it is thus possible for the shipmas¬ ter to receive uninterrupted readings on the display 33. Experience has shown that assessment of the appliance setting by means of the readings displayed only is a skill quickly acquired. Preferably, the control unit comprises a voltmeter and the readings equal the voltage measured. The control unit may comprise processing equipment allowing for reading of the distance between the wires measured as cm per m extended wire. The control unit may moreover comprise acoustic alarms (not shown) emitting a signal immediately to the shipmaster, should the mutual angle setting of the wires reach predetermined marginal values.