GB2036127A

GB2036127A - Pick Assembly

Info

Publication number: GB2036127A
Application number: GB7848637A
Authority: GB
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1978-12-15
Filing date: 1978-12-15
Publication date: 1980-06-25

Abstract

A pick assembly for a rotary head mining machine, e.g. a shearer, comprises a leading pick box, 2, and a trailing pick box, 3, so arranged that a pick, 4b, in the trailing pick box will make a shallow and constant penetration cut, an actuator, 13, extending through a hole, 12, in the trailing pick box and a piezoelectric sensor, 16, in contact with the actuator, whereby pivotal movement of a pick in the trailing pick box during cutting is transmitted by the actuator to the sensor, and a signal generated indicative of the load on the pick in the trailing pick box. The assembly permits easy servicing and replacement of the sensor in the event of failure. <IMAGE>

Description

SPECIFICATION Pick Assembly This invention concerns mineral mining machines having picks mounted on a cutter, more particularly it concerns a pick assembly having means for determining the position of the cutter relative to a boundary of a mineral seam.

It is known for a pick to be resiliently mounted in a rotary cutter, for example in the drum of a shearer, and to provide means sensitive to the movement of the pick under varying cutting loads.

The aim of such arrangements is to sense the load on the pick, which varies according to the type of mineral being cut and on the penetration of the pick into the mineral, to enable the mining machine to be steered to cut only desired mineral and not adjacent rock. Our British Patent No.

1,219,159 illustrates an advanced type of pick load sensor, in which a cutter tool or pick is resiliently mounted on the rotary head of a rotary cutter, and the relative movement between the resiliently mounted pick and a fixed pick is sensed. In practice it has been found that while the invention of Patent 1,219,159 is effective, the immense and varying loads on the resilient mounting can cause failure of the mounting, and the assembly as a whole is time consuming to repair or service.

The present invention provides a pick assembly for a rotary head mining machine having picks fixedly mounted on and distributed around the rotary head, which assembly comprises a leading pick box and a trailing pick box, so arranged that a pick in the trailing pick box will make a shallow and constant penetration cut, an actuator extending through a hole in the trailing pick box and a piezoelectric sensor in contact with the actuator, whereby pivotal movement of a pick in the trailing pick box during cutting is transmitted by the actuator to the sensor, and a signal generated indicative of the load on the pick in the trailing pick box.

Preferably, the hole is in the front (leading edge) of the trailing pick box. It is preferred that the piezoelectric sensor is mounted in a plug-in sensor assembly, which is easily replaceable in the event of failure. The signal generated may be transmitted to a manual or automatic cutting control location by a cable extending through the hub of the rotary head, or by a miniature radio transmitter.

The invention is herein described with particular reference to installations in coal mines, but it is to be understood that the invention is applicable to analogous mining uses.

The invention will now be described by way of example only, with reference to the accompanying drawing which shows a part section of a pick assembly according to the invention, mounted on the cutter drum of a shearer.

The cutter drum of a shearer is represented by 1; fixed onto the outer edge of the drum, for example by welding, are a leading pick box 2 and a trailing pick box 3, each shown carrying standard picks 4a, 4b. The picks 4a, 4b are retained in the boxes by standard fixings such as retaining pins (not shown). The trailing pick box is close behind and in line with the leading pick box, and is at a greater radial distance from the axis of the cutter drum. Such an arrangement has been proposed before and permits the pick in the trailing pick box to make a constant cut of for example 1.27cm 11/2 inch).

Mounted between the pick boxes and also fixed onto the cutter drum is a housing 5, having a central bore 6 extending most of its length. At the bottom of the bore is recess 7, into which a connector element 8, having jack plug 9, fits. The connector element 8 is retained in the recess by pins 10, and a lead 1 1, is led out of the bottom of housing 5.

Between the front of the trailing pick box 3 and bore 6, extends a cross bore 12, and slidably fitted within the cross bore is a two-part hardened steel actuator 13. A sensor housing 14 slides into bore 6 and has a spring-loaded female connecter element 15 for engagement with jack plug 9. A piezoelectric sensor 16 is fitted into the housing and is conveniently screwed into position or cemented into position using adhesive; the signal lead 17 from the sensor extends within the sensor housing to the female connecter element 15. A suitable piezoelectric sensor 16 is the 200 A20 Impact Transducer manufactured by PCB Piezotronics Inc. of Buffalo, New York, marketed in the United Kingdom by Technimeasure, Dell House, Eastern Dene, Hazlemere, High Wycombe, HP 1 5 7BT.The sensor housing 14 is suitably provided with means (not shown) to permit its insertion in only the correct orientation, so that actuator 13 contacts the face of sensor 16 and extends through the cross bore to the inner face of trailing pick box 3 and also contacts the shaft 20 of the pick 4b. The sensor housing 14 is retained in bore 6 against the action of the springloaded female connecter element by means of cap 18, which in turn is retained by a pin 19 extending therethrough and through housing 5.

In use, a cutter drum for a shearer, or a trepanner cutter head, may have one, two or more pick assemblies according to the invention.

During operation of the cutter head, the pick 4b cuts behind pick 4a, and makes a constant shallow cut. Should the cutter head cut into the roof or floor and thus cut rock instead of coal, the different hardness will result in a different load upon the picks. As the picks cut, the load on the tips cause a pivotal movement, forcing the bottom of the pick shaft forward. In the case of pick 4b, shaft 20 acts upon the actuator which in turn transmits the force to the piezoelectric sensor. The signal generated is transmitted through lead 11 to a control location. The instantaneous position of the pick assembly according to the invention, i.e. its position on the cutter head for each sensor signal is preferably recorded in known manner. Machine steering and relevant control mechanisms and circuits are disclosed in our Patent No. 1,219,159.

In the event of a failure in the sensor, it is quick and simple to rectify. The pick in the trailing pick box is withdrawn, enabling the actuator to be pushed aside and the sensor housing easily withdrawn for replacement.

This is an appreciable step forward in this art. If dirt etc. prevent easy extraction of a failed sensor, the sensor housing may be provided with screw holes in its top into which an extractor may be fitted.

Claims

1. A pick assembly for a rotary head mining machine having picks fixedly mounted on and distributed around the rotary head, which assembly comprises a leading pick box and a trailing pick box, so arranged that a pick in the trailing pick box will make a shallow and constant penetration cut, an actuator extending through a hole in the trailing pick box and a piezoelectric sensor in contact with the actuator, whereby pivotal movement of a pick in the trailing pick box during cutting is transmitted by the actuator to the sensor, and a signal generated indicative of the load on the pick in the trailing pick box.

2. An assembly according to claim 1, wherein the hole is in the front of trailing pick box.

3. An assembly according to claim 2, wherein the sensor is mounted in a sensor housing which is replaceably fitted between said leading and trailing pick boxes.

4. An assembly according to claim 3, wherein the sensor housing is provided with a first connector element which co-operates with a second connector element to transmit the signal from the sensor.

5. An assembly according to claim 1, substantially as hereinbefore described with reference to the drawings.