This invention relates to a device for use with a tractor-carried container which enables the container load to be monitored.
Seed drilling and fertilizer spreading is often carried out using a hopper attached to the rear of a tractor on a cantilevered frame. Support for the hopper is typically provided by a lower beam, which can be raised and lowered by a hydraulic mechanism on the tractor and about which the hopper is pivotable, and a top link in the form of a load-bearing turnbuckle which is under tension and which can be used to adjust the angular position of the hopper.
In seed drilling or fertilizer spreading, it is important to spread the seed or fertilizer in the correct amount per unit area. For example, the most usual method of drilling is to allocate a weighed trailer load of seed to the area to be drilled on the basis of the intended seed rate in Kg/hectare. The drill manufacturer""s calibration routine may have been carried out on a proportion of the seed outlets in preparation. The seed is transferred in the field from the trailer to the drill hopper by means of an auger and sowing begins. The hopper is replenished as-necessary and a tally is kept of the number of refills. Checking the number of refills against the hectare meter of the tractor gives some indication of seed rate, but it is difficult to estimate how much seed is left in a partly full hopper so that the true seed rate can only be determined when the trailer is empty. This process generally necessitates adjustments to the seed flow from time to time so that although the overall intended seed rate may be achieved the distribution may be uneven. There is therefore a need for a weighing mechanism which will give an indication of the amount of seed or other material left in the hopper at any given time.
DE-A-3714642 describes an agricultural spreader carried on a tractor tool frame by a three-point lifting device. A top link of the lifting device, which is under tension, incorporates a weighing device to monitor the weight of the load in the spreader and the rate of spreading. A problem which arises with the use of such a tension link as a weighing device is that the measured weight may vary according to the angular orientation of the link. In particular, the weight distribution over a three-lifting device may vary according to whether the tractor is on level ground or on a slope.
EP-A-407705 discloses a three-point lifting device for a tractor-mounted hopper in which the weight of the hopper is measured by sensors at each of the three load-bearing points of the device. The angular orientation of the device is also sensed and a signal is fed to a microprocessor together with signals from each of the three weight-sensors.
EP-A-537857 and EP-A-797082 also disclose lifting devices incorporating a strain gauge or other weight sensor and an angle measuring cell arranged to correct measured weight values to compensate for the angular position of the tractor and container.
The present invention provides a device for monitoring a load in a container being towed or carried by a tractor or other vehicle, the device comprising one or more strain gauges to provide a signal indicative of the load at a position remote from the device and a level indicator adapted to give a signal indicative of the angular orientation of the device relative to the horizontal, characterised in that the strain gauge or gauges and the level indicator are incorporated together in a tension link securable to the container as part of a towing or support mechanism therefor, such that the tension in the link is dependent on the weight of the load in the container, the signal provided by the strain gauge being indicative of the tension in the link and the level indicator being mounted in the tension link so as to be rotatable relative thereto about a horizontal axis, to set an orientation for calibration of the device.
The device of the invention is preferably in the form of a top link extending between a tractor and the container, for example a hopper which is pivotally mounted on a cantilevered frame. The link is preferably in the form of a turnbuckle so that the angular position of the container can be adjusted.
The link preferably includes a load cell, comprising an array of strain gauges, arranged to provide an indication of the tension in the link, to be displayed in a cab of the towing or carrying vehicle. The display can be calibrated with the container both empty and filled with a known quantity of specified material such as particular seed or fertilizer, with the same orientation of the device as shown by the level indicator, so that the tension reading gives an indication of how much remains in the container at any given time. The tension data can also be used, with the aid of a suitable microprocessor, to provide an indication of the rate at which material is being distributed from the container, by linking the measured load in the container, and its rate of depletion, with the speed of the vehicle and the area being swept by it.
A rough reading can be displayed continuously, with more accurate readings being taken from time to time by stopping on relatively level ground and using the lifting device to set the tension link at the predetermined orientation at which calibration took place.