Abstract:
A method and apparatus for preventing the unexpected loss of heavy mining equipment by detecting the separation of heavy metal parts at an early stage in the separation process, and providing a warning signal in response to which the particular machine that is having the difficulty may then be shut down in a timely manner. A spring-loaded switch is sandwiched between the heavy metal parts, which upon partial separation of the parts then expands and turns on an electrical switch to activate a radio transmitter, sending an alarm signal to a receiver at a remote location.

Description:
PRIORITY CLAIM 
   This application claims the benefit of our U.S. Provisional Application No. 60/263,933 filed Jan. 24, 2001. 

   FIELD OF THE INVENTION 
   This invention relates to the control and safety of heavy equipment used in the mining industry. 
   BACKGROUND OF THE INVENTION 
   In open-pit mining operations it is common practice to utilize very large machines. One such typical machine is a hydraulically operated digging machine or shovel that includes a huge bucket equipped with a number of metal teeth. The bucket has a leading edge on which the metal teeth are carried, and during the operation of the machine the teeth are pushed into hard earth and rock to recover the ore. The teeth are typically made of very hard steel but are replaceable because they wear down during usage. 
   In some such equipment a separate metal piece, called an adapter, is used to mount each tooth on the leading edge of the bucket. The adapter is also a replaceable item. In that type of equipment the adapter is attached by pins or otherwise to the leading edge of the bucket, and the tooth is attached by pins or otherwise to the adapter. 
   Other forms of the equipment, however, do not use a separate tooth adapter, the tooth structure then being integrally formed to include both a tooth portion and an adapter portion. The tooth structure is therefore extremely large and attached directly to the leading edge of the bucket. 
   A problem which has occurred from time to time is that a portion of the steel tooth structure—a steel tooth, an adapter, or some combination thereof—may become separated from the bucket to which it is normally attached, and may then be carried away with the ore in a haul truck to the ore crusher. Because of the huge size of the haul trucks a steel tooth structure weighing a ton or more can pass unnoticed into the ore crusher. The hard steel of the tooth structure cannot be easily pulverized by the crusher, with the result that the crusher itself is seriously damaged. 
   Such damage to the ore crusher not only requires repair of the crusher itself, but may require shutting down an entire operation, perhaps including numerous digging machines, entailing a very large financial loss before the operation can be resumed. A single shut-downs may involve a loss in excess of a million dollars. 
   SUMMARY OF THE INVENTION 
   According to the invention the unexpected loss of heavy mining equipment is prevented by detecting the separation of the metal parts at an early stage in the separation process, and providing a warning signal in response to which the particular machine that is having the difficulty may then be shut down in a timely manner. 
   According to the presently preferred form of the invention the detection of partial separation of the metal parts is accomplished by a spring-loaded switch sandwiched between the parts, which upon partial separation of the parts then expands and thus turns on an electrical switch to activate a radio transmitter. 

   
     DRAWING SUMMARY 
       FIG. 1  is a perspective view of a typical mining shovel, with its bucket and steel teeth, one tooth for purpose of illustration being shown in a removed position; 
       FIG. 2  is a cross-sectional elevation view taken on the line  2 — 2  of  FIG. 1 , showing the leading edge of the bucket together with an adapter and an associated steel tooth that it supports; 
       FIG. 3  is a fragmentary cross-sectional elevation view of the interengaging surfaces of the bucket leading edge and the adapter, taken on line  3 — 3  of FIG.  2  and showing an electromechanical transducer installed in a recess in the surface of the bucket in accordance with the present invention; 
       FIG. 4  is a fragmentary horizontal cross-sectional view taken on line  4 — 4  of  FIG. 3 , showing some internal details of the electromechanical transducer; 
       FIG. 5  is a cross-sectional view similar to  FIG. 2 , but showing the adapter separated from the bucket after its attachment pin has broken; 
       FIG. 6  is a fragmentary vertical cross-sectional view taken on the line  6 — 6  of  FIG. 5 , showing other internal details of the electromechanical transducer; and 
       FIG. 7  is a fragmentary view of the instrument panel inside the operator&#39;s cab of the shovel machine, showing alarm devices associated with the radio receiver. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   FIGS.  1 - 7   
   In general, the unexpected loss of a tooth structure is prevented by detecting its separation from the leading edge of the bucket, at an early stage in the separation process, and providing a warning signal to the operator&#39;s cab of the machine so as to allow the operator to shut down the machine in a timely manner. 
   Further according to the presently preferred form of the invention, an electromechanical transducer is in the form of a spring-loaded switch sandwiched between the metal parts, which upon partial separation of the metal surfaces expands and turns on an electrical switch to activate a radio transmitter. 
   An adapter presents a more serious problem to the ore crusher than does a steel tooth by itself, because a lost adapter carries a tooth with it. In present machines the adapter alone may weigh over a ton. Therefore, according to the presently preferred form of the invention the electromechanical transducer detects partial separation of an adapter from the leading edge of the bucket on which it is carried. 
   More specifically, the electromechanical transducer in its presently preferred form is contained within a recess in the surface of the leading edge of the bucket, and engages an inner surface of the adapter. The transducer in that position is then fully protected from the movement of earth and rock that impinges upon the surfaces of the steel tooth and adapter during the ore digging process. 
     FIG. 1  shows the digging machine or shovel  10  with operator&#39;s cab  12  and bucket  14 . An adapter attachment opening  15  is formed in the bucket  14  near its forward end. The leading edge of the bucket is designated as  16 . Although not specifically shown in  FIG. 1 , the leading edge  16  of the bucket  14  carries a number of adapters  22 . Each adapter  22  in turn supports a tooth  32 . In a typical machine there may be as many as twelve adapters, and hence twelve teeth, carried on the bucket  14 . Adapters  22  may be removed from the bucket  14  for the purpose of replacement, and teeth  32  are also removable from the adapters  22  for purpose of replacement. 
   The leading edge  16  of the bucket  14  has a plurality of recesses  17 , one for each tooth  32 . According to the presently preferred form of the invention a transducer housing assembly  40  is contained within each such recess  17 . 
   Each adapter  22  has upper and lower legs  23 ,  25 , which fit around the leading edge  16  of the bucket  14 . Upper leg  23  has a hole  24  therethrough, while lower leg or flange  25  has a hole  26  therein. An adapter attachment pin  20  secures each adapter  22  to the leading edge  17  of bucket  14  through the aligned holes  24 ,  26 . 
   Each recess  17  in the leading edge  16  of the bucket  14  is fitted with a transducer housing assembly  40  and electromechanical transducer, as shown more in detail in  FIGS. 3 ,  4 , and  6 . Of particular note is the under surface  23   b  of the upper leg  23  of adapter  22 , because that is the surface in conjunction with which the electromechanical transducer operates. 
   Transducer housing assembly  40  includes an outer steel can  41  and an inner aluminum can  42 . Aluminum can  42  has a plastic cap or cover  44  that mechanically protects the electrical circuitry within the housing assembly while permitting radio signals to escape to the exterior. The steel can  41  is welded in place as shown at  46 . Inner can  42  is supported within the outer can by upper and lower grommets  47 ,  48 , to protect the contents from excessive shock and vibration when the mining machine is in operation. The aluminum inner can  42  is removably inserted into the steel can  41 . The use of a housing assembly of this kind provides a convenient modular concept in the installation and replacement of transducers. 
   Each transducer assembly  50  is housed within the aluminum inner can  42 . A plunger housing  43  is also associated with and contained within the inner can  42 . A flat printed circuit board  54 , best seen in  FIGS. 3 and 4 , divides the interior of the aluminum can into two semi-cylindrical compartments. One such compartment receives a battery  56  and circuit board  54  while the other compartment receives the plunger housing  43 . 
   The plunger housing  43  made of aluminum is in the form of an elongated cylinder with a large cylindrical opening in its bottom portion and a smaller cylindrical opening in its upper end. Cylindrical plunger  51  is slidably received within the smaller upper opening of housing  43 . In the bottom portion of housing  43  a steel coil spring  52  is received, and a magnet  53  rests upon the top end of the coil spring.  FIG. 3  shows the closed or retracted position of the plunger  51 , while the adapter  22  remains attached in its normal operative position to the bucket, in which the spring  52  is compressed and plunger  51  engages the inner and under surface  23   b  of upper leg  23  of the adapter  22 . 
   Battery  55  has wires connected to a switch  56 , which is installed in or associated with the flat printed circuit board  54 . An antenna circuit  57  is wired onto the side wall of circuit board  54  that faces toward the plunger compartment. Closing of the switch  56  will complete a circuit between battery  55  and antenna  57 , to cause the antenna to generate a radio signal at a predetermined frequency. 
   The plunger housing  43  is spaced somewhat away from the circuit board  54 . The battery  55 , wires  58 , and switch  56  in the battery compartment are encased in a floating relationship in a body of silicone  59 , commonly known in the electronics industry as potting compound. Material of the same kind also fills spaces around the plunger housing  43 . 
   The nature of switch  56  is that whenever the magnet  53  moves upward past the switch, even though there is no mechanical contact, the relative movement of the magnet causes the switch to close electrically, thereby energizing circuit board antenna  57 . 
   The transmitters in all of the detector units are preferably set to operate at the same frequency to send signals  60 , since the receiver  62  ( FIG. 7 ) is most conveniently set to operate at only a single specified frequency. There is no need, however, to code the transmitter frequencies, since once the operator is alerted to the trouble by alarm device  65 , he can determine visually which one of the adapters is breaking loose. 
   Each tooth  32  has upper and lower legs  33 ,  34 , that fit over the nose  28  of the associated adapter, and the tooth is then secured by an attachment pin  30  through tooth attachment opening  29  to the associated adapter. 
   Operation 
   When adapter  22  starts to break loose from the leading edge of the bucket  14 , the pressure on the outer end of plunger  51  is relieved, and the plunger then tends to fly outward, as shown in FIG.  6 . During that movement the spring  52  expands, and magnet  53  moves past the switch  56 , causing switch  56  to close. Closing of the switch causes the battery  55  to energize the antenna  57  on the circuit board  54 . Once the plunger clears the opening of its housing, the antenna output signal  60  is freely transmitted through plastic cap  44  into the surrounding atmosphere, and reaches the operator&#39;s cab  12 , where it is received by receiver  62 . 
   As shown in  FIG. 7 , the operator&#39;s cab is equipped with various alarm devices  65 , both visual and aural, to inform the operator that an adapter is breaking loose. If loss of the adapter cannot be stopped, its tooth will go with it to the ore crusher. 
   Modified and Alternative Forms 
   It is not essential that the transmitter of each alarm unit be constructed integral with the associated mechanical part: Various kinds of electromechanical or electromagnetic transducers may be used to carry out the concept of the invention. 
   While we have disclosed the presently preferred embodiment of our invention in detail in order to comply with the requirements of the patent laws, it is to be understood that the scope of the invention and the protection herein sought is to be determined only in accordance with the appended claims.