Abstract:
A vibratory system for a vibration feeder includes pulse means for generating electrical digital pulse signals. A controller controllably converts the electrical digital pulse signals either into an incrementally increasing or decreasing DC voltage level. At least one vibration block is coupled to the controller for being increased or decreased in its amplitude of vibration in response to the respective incrementally increasing or decreasing DC voltage level generated by the controller. A remotely located additional controller, such as a programmable logic controller, may be coupled to the controller for transmitting electrical digital pulse signals to control the amplitude of vibration.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a vibratory system, and more particularly to a vibratory system for a vibratory parts feeder. 
     BACKGROUND OF THE INVENTION 
     Vibration systems are conventionally used in manufacturing to correctly orient and deliver small items such as plastic covers to assembly lines. Such systems typically include a vibratory bowl, the vibration of which is controlled by a controller. 
     Conventional systems have a number of associated problems. Firstly, the controllers of the system are typically on/off switches which do not allow for the system to be fine-tuned for specific applications. Secondly, adjustment of the vibration parameters is achieved by manual adjustment of the vibratory blocks. These blocks are typically located underneath the vibratory bowl or the like and are often difficult to access. 
     Accordingly, it is an object of the present invention to provide a vibratory system which overcomes the above-mentioned drawbacks and disadvantages. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, a vibratory system for a vibration feeder includes pulse means for generating electrical digital pulse signals. A controller controllably converts the electrical digital pulse signals either into an incrementally increasing or decreasing DC voltage level. At least one vibration block is coupled to the controller for being increased or decreased in its amplitude of vibration in response to the respective incrementally increasing or decreasing DC voltage level generated by the controller. 
     More specifically, the controller includes an adjustment function for varying the vibration parameters of the vibration system, and may include a save function to save the vibration parameters. 
     As mentioned above, the adjustment function typically allows the amplitude of the vibration of the system to be controlled. This allows a user to accurately set and control the vibration system. 
     Typically, the adjustment of the amplitude is incremental. The increments are preferably small values. This allows the vibration system to be finely tuned for a specific application. 
     The adjustment function typically includes an increment button, an up/down button and a save button. 
     Preferably, the adjustment function includes a feedback system. This allows for automatic adjustment of the vibration parameters to maintain a constant output. The feedback system typically comprises a transducer, the transducer being coupled to the vibration system to measure the amplitude and/or frequency of vibration. The transducer is preferably a solid state transducer. This reduces the possibility of failure as there are no moving parts, thus increasing the lifecycle and reliability of the controller. 
     The save function typically allows a user to save the latest parameters of the vibration system. Thus, when the system is powered down (i.e., switched off) the latest parameters are stored for subsequent retrieval when the system is powered up (i.e., switched on). 
     Optionally, the controller includes a display for displaying the vibration parameters. Preferably, the display is a digital display. This allows for more accurate readings and aids the user in setting up the vibration system. 
     Optionally, the controller further includes indicia for indicating the status of the controller. The indicia typically comprises light emitting diodes (LEDs). Typically, a green LED indicates that the system is running, and a red LED indicates a fault in the system. 
     Optionally, a remote controller may be coupled to the control to remotely control the functions of the controller. The remote controller is typically provided with an increment button, an up/down button and a save button. The remote controller optionally includes a display for displaying the vibration parameters. The remote controller optionally includes indicia for indicating the current status of the controller. 
     According to a second aspect of the present invention there is provided a vibratory block comprising a pair of end plates, at least one pair of springs attached to opposite edges of said end plates, and vibration means, characterized in that the springs comprise composite springs. 
     The composite springs are preferably flat, leaf springs. The composite springs typically comprise a plurality of glass filaments. Preferably, 85-90% of the filaments are oriented in the bending or primary direction, and 10%-15% of the filaments are oriented perpendicularly to the primary direction. 
     The vibration means typically comprises an electromagnet. 
     Embodiments of the present invention shall now be described with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic circuit diagram of a logic board for use with the controller embodying the present invention. 
     FIG. 2 is a schematic circuit diagram of a power board for use with the controller of FIG.  1 . 
     FIG. 3 is a front view of a housing for the controller of FIG.  1 . 
     FIG. 4 is an exploded view of a vibratory block according to a second aspect of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a schematic circuit diagram of a logic board which forms part of a controller  10  embodying the present invention. The controller  10  powers and controls the vibration of a vibratory parts feeder. 
     The logic board includes an example of circuitry for implementing the various functions of the controller  10 . FIG. 2 shows a schematic circuit diagram of a power board which forms part of the controller  10  of the present invention. The power board includes an example of circuitry for selecting between various input voltages (i.e., for selecting either 115 volts ac or 230 volts ac). 
     Referring now to FIG. 1, the logic board of the controller  10  includes a digitally controlled potentiometer  11  which also functions as an electrically erasable programmable read-only-memory (EEPROM). To control the vibrating system, the amplitude of a sine wave applied through silicon controlled rectifier (SCR)  12  (FIG. 2) to a vibrating block (see FIG. 4) may be varied. This change in amplitude in the sine wave results in an increase in the amplitude of vibrations at the vibratory block. 
     A first push button switch  16  (increment) allows the amplitude of the sine wave to be increased by transmitting a digital pulse to the potentiometer  11  each time the push button switch  16  is depressed. More specifically, when the first push button switch  16  is depressed, pin  1  of the digitally controlled potentiometer  11  goes low, causing the output of an operational amplifier  18  to increase. This increase in output voltage at the operational amplifier  18  changes the pulse to a transistor  20 , the output of which is coupled to the gate of the SCR  12  such that the SCR  12  is triggered on earlier in a firing cycle. The earlier triggering of the SCR  12  causes an increase in the voltage across a vibratory block (not shown) which is connected to the terminals H 1  and H 2  on junction strip  22  (FIG.  2 ), thus causing the amplitude of the vibrations at the vibratory block to increase. Repeated depression of the first push button switch  16  causes the amplitude of vibration to be increased an incremental amount for each depression of the push button switch  16 . 
     A second push button switch  24  (up/down) is used to control the function of the first push button switch  16 . If the first push button switch  16  is depressed alone, then the vibrations at the vibratory block will incrementally increase for each depression of the push button switch  16  as described above. If the second push button switch  24  is pushed and held depressed, then the amplitude of the vibrations at the vibratory block will decrease an incremental amount for each depression of the first push button switch  16  while the second push button  24  is held depressed. 
     Thus, when the first push button switch  16  is repeatedly depressed while the second push button  24  is held depressed, the inputs to pins  1  and  3  of the digitally controlled potentiometer  11  go low. Consequently, the output voltage at the potentiometer  11  (pin  5 ) reduces, causing the firing point of the SCR  12  to be later in its firing cycle. This reduces the potential across the vibratory block and the amplitude of the vibrations. 
     A single depress of the first push button switch  16  changes the current to the gate of the SCR  12  by, for example, between 0.125 and 0.2 amps. This change in current results in an increase of amplitude of vibration of the vibratory blocks about twenty thousandths of an inch (0.58 mm). A similar reduction in current and amplitude of vibration results when the first push button switch  16  is depressed while the second push button switch  24  is held depressed. 
     To avoid having to reset the amplitude of the vibrations after power to the controller  10  is switched off, a third push button switch  26  is coupled to the digital potentiometer  11  so as to store the current parameter settings of the vibration amplitude level in the EEPROM memory of the digitally controlled potentiometer  11 . Thus, when the controller  10  is switched off and then switched back on, the controller will automatically re-initialize to the vibration amplitude level previously set before the third push button  26  was depressed. 
     Optionally, a display screen such as a liquid crystal display (LCD)  60  may be used to monitor the amplitude level of vibration. Thus, when an increase or decrease in amplitude of vibration is desired, the first and second push button switches  16 ,  24  are depressed accordingly and the amplitude of the vibrations is displayed on the LCD  60 . This allows the level of amplitude of vibration to be monitored and set more accurately. Conventional controllers use an analog scale to set the amplitude which is less accurate and relies on a user correctly interpreting the value from an analog display. 
     A conventional solid state accelerometer or transducer (not shown) is coupled to the vibrating block. The transducer produces an AC sine wave which is proportional to the vibrations at the vibratory block. The AC peak voltage is converted to a DC voltage by a converter circuit, generally designated  44  in FIG.  1 . The DC voltage is used as a reference voltage for servo control, the DC voltage being applied to the operational amplifier  18  which is configured in comparator mode. Thus, the controller  10  will automatically keep the amplitude of vibration substantially constant. 
     Conventional vibratory systems use a photoelectric interrupter transducer (not shown) which typically comprise a light emitting diode (LED) and a phototransistor which face one another across a slot. A pin or the like is mounted to the vibratory block wherein movement of the block moves the pin in the slot, thus interrupting the beam between the LED and the phototransistor. As the vibrator oscillates, the phototransistor is alternatively light and dark which provides an amplitude dependent signal to the controller. 
     These mechanical transducers are not as reliable as solid state transducers because they have moving parts and are prone to failure. In addition, the amplitude dependent signal is not always accurate. Further, the amplitude of vibration using such mechanical transducers cannot be controlled from a remote location. 
     In order to increase the accuracy and lifetime of the transducer, a solid state transducer (not shown) is used. The transducer is coupled to a junction  46  on the power board (FIG.  2 ). Unlike the conventional filtered transducer signal which is often slow, or the use of sample and hold circuits with fixed duration and trigger times, solid state transducers are more tolerant of electrical noise and phase shift. Thus, more reliable control of the system can be achieved in harsh industrial environments. 
     In addition, the transducer allows the mechanical condition of the vibratory block to be monitored, even from a remote location using, for example, a smart controller such as a programmable logic controller  36  (PLC). One sign of impending failure of a vibratory block is a decrease in the mechanical resonant frequency. It has been found that a vibration block works at peak performance when its resonant frequency is tuned slightly above the frequency of the AC line voltage powering the block. For example, an optimal frequency of resonance is about 61.5 Hz to about 62.0 Hz for an AC line frequency of 60 Hz. As the vibration block begins to wear, the frequency of vibration begins to approach the line frequency and then becomes lower than the line frequency. 
     The controller  10  determines when the frequency of vibration falls below the AC line voltage by indicating a fault condition by means of fault circuitry enclosed by the line  34 . The fault circuitry compares the AC line signal and the sinusoidal signal derived from the transducer or accelerometer coupled to the vibration block. The AC line signal is modified for phase comparison with the transducer signal by being sent through a zero crossing detector generally designated as  35 . The modified AC line signal after passing through the zero crossing detector is in the shape of a square wave. The modified line signal is then delayed 90° at a delay stage generally designated as  37 . The modified line signal is then translated into a signal having a slope at a ramp stage generally designated as  39 . The slope which is a function of the number of digital pulses generated by the pushbutton switch  16  or a remote controller is what is compared to a DC level signal from the transducer. The lower in voltage the signal coming from the transducer, the earlier in the cycle the SCR  12  will be triggered based on a predetermined setting of the digital potentiometer  11 . The phase angle of the signal from the transducer is compared with the phase angle of the AC line voltage. A transducer lagging phase angle resulting from the frequency of vibration dropping below the line frequency indicates that maintenance of the vibratory block may be required. 
     To monitor the status of the controller  10 , two light emitting diodes (LEDs)  30 ,  32  are provided. LED  30  is typically a green LED and indicates that the vibratory block is running. LED  32  is typically red and indicates that there is a fault in the system resulting from the lowered frequency of vibration. A timer circuit generally designated  34  in FIG. 1 controls the operation of the LEDs  30 ,  32  causing them to pulse rather than light continuously to conserve power. 
     The controller  10  includes an interface for controlling the amplitude of vibration remotely by means of an additional intelligent controller, such as a programmable logic controller  36  (PLC), (not shown) which is coupled to a junction  28  on the power board (FIG.  2 ). The remote intelligent controller allows a user to increase or decrease the amplitude of the vibrations remotely. The status of the controller  10  may also be displayed on the remote intelligent controller by using similar LEDs to the LEDs  30 ,  32 . Optionally, the amplitude of the vibrations may be displayed on an LCD on the remote controller. The circuitry of the remote intelligent controller is isolated from the circuitry of the controller  10  using opto-isolators  38 ,  40 ,  42  (FIG.  2 ). The opto-isolators  38 ,  40 ,  42  isolate the increment and up/down switches on the remote intelligent controller and also the status LEDs. Note that the remote intelligent controller may be used without digital to analog conversion, thus reducing the over-all cost and complexity of the controller. The digital pulses generated by the PLC  36  simulate a more complex and expensive analog control circuitry otherwise required to adjust the amplitude of vibration from a remote location. 
     Relay outputs on junction  50  (FIGS. 1 and 2) indicate that the vibratory block is vibrating and can be used to control other equipment, such as line feeders, vibrating lines or the like, or may be used to signal the remote intelligent controller. 
     Input to the controller  10  is typically single phase line neutral and earth ground. Output from the controller  10  is typically single phase half wave. The controller  10  includes a transformer circuit generally designated  48  in FIG.  2 . The transformer circuit  48  allows the controller  10  to be operated from 115 or 230 volts AC. The input voltage is selected using jumpers. This provides a more versatile controller. 
     FIG. 3 shows a typical housing  13  for the controller  10  of the present invention. FIG. 3 is a front view of the housing  13 , showing the LCD display  60 , the status LEDs  30 ,  32  and also the push buttons  16 ,  24  and  26 . 
     Referring now to FIG. 4, a vibratory block is generally designated by the reference number  100 . The vibratory block  100  comprises a pair of heavy end plates  102   a ,  102   b  which are coupled together by at least one pair of composite leaf springs  104   a ,  104   b . The springs are separated from the end plates  102   a ,  102   b  (and from each other if more than one pair is used) by a pair of spacers  106 . 
     One of the end plates  102   a  has an encapsulated coil and iron core generally designated  108  coupled thereto, which forms part of an electromagnet. The opposite end plate  102   b  has an armature  110  coupled thereto. The air gap between the encapsulated coil and iron core  108  and the armature  110  is adjustable. The springs  104   a ,  104   b  and spacers  106  are mounted to the end plates  102   a ,  102   b  using clamp bars  112  and mounting screws  114 . 
     One or more pairs of springs  104   a ,  104   b  are used, depending upon the weight of the vibratory equipment which the vibratory block  100  is to drive. The spacers  106  between the end plates  102   a ,  102   b  and the springs  104   a ,  104   b  are used to reduce friction and to prevent fretting corrosion at the clamped end. 
     The composite springs  104   a ,  104   b  are preferably manufactured from continuous glass filaments which are oriented in a particular manner. Approximately 85-90% of the filaments are oriented longitudinally in the bending or primary direction. However, 10-15% of the filaments are positioned just under the surface and are oriented to be approximately perpendicular to the longitudinal filaments. This increases the strength of the spring  104   a ,  104   b  in the “cross” direction. 
     Composite springs  104   a ,  104   b  provide a number of advantages. Firstly, the springs  104   a ,  104   b  give improved pressure distribution. Secondly, the springs  104   a ,  104   b  have a longer lifetime. Thirdly, composite springs  104   a ,  104   b  can move further; that is, conventional steel springs can flex approximately one quarter of an inch (approximately 6.25 mm), whereas the composite springs  104   a ,  104   b  can flex about 0.32 inches (about 8 mm). This amplitude difference is advantageous vibratory equipment, and gives a wider range of vibration. In addition, composite springs  104   a ,  104   b  can store more energy and thus reduce the mount of current required to drive the vibratory system, making the system more efficient. 
     Thus, there is provided a controller  10  for a vibration system which is versatile and offers many advantages over conventional systems. The controller  10  may be used to set the amplitude of vibration of at least one vibratory block, which may then be stored for subsequent retrieval. Other features include the possibility of remote control. 
     There is also provided an improved vibratory block for use with vibration systems. The vibratory block uses composite springs which provide many advantages over conventional steel springs. 
     Although this invention has been shown and described with respect to an exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions in the form and detail thereof may be made therein without departing from the spirit and scope of the invention. For example, Accordingly, the present invention has been shown and described by way of illustration rather than limitation.