Patent Grant
8096406
The present invention is related generally to a system and method for advancing an article on a vibratory conveyor and more specifically to a system and method for controlling the retention time of an article being conveyed by selective and directional application of a vibratory force to a conveyor as a function of at least one sensed variable.
There are known in the art a plurality of commercially available vibratory conveyor systems for controlling the speed and direction of articles or materials being conveyed thereby. Many prior art systems vary conveying speed and direction by changing either the direction or magnitude of a force applied to a conveyor trough that is resiliently mounted on a suspension system to permit vibratory motion to be imparted thereto. Alternative prior art conveying systems employ a wide variety mechanical systems to elevate or decline an end of the vibratory conveyor, thereby changing the angle of inclination of the entire conveyor trough to speed up or slow down the progress of an article along the conveyor.
One exemplary prior art system of this nature is U.S. Pat. No. 5,615,763 to Schieber, assigned to Carrier Vibrating Equipment, Inc., of Louisville, Ky., herein incorporated by reference. Generally speaking, this systems varies the vibratory force being applied to a resiliently mounted conveyor trough by securing to the trough a plurality of shafts having a plurality of eccentric weights mounted thereto. The shafts, and consequently the eccentric weights, are capable of rotation, typically through the action of driven pulleys or the like such that the rotating shafts and eccentric weights impart a vibratory force to the conveyor trough.
The angle of the vibrating force acting on the conveyor in such systems is determined by the relative position of the eccentric weights on the rotating shafts. The relative position, or phase angle relationship between eccentric weights may be maintained and controlled by various mechanical control and positioning systems or alternatively, by utilizing an electronic control system to monitor and adjust the phase angle relationships between various rotating masses.
Prior art vibratory conveyor systems are incapable of monitoring an article being conveyed to adjust the speed and direction of conveyance to impart a desired amount of vibratory force to an article before its discharge from the conveyor. The ability to monitor an article's position or progress along the conveyor can be very beneficial for certain products and manufacturing processes that require the input of a particular amount of force over a given time period for proper production. For example, some casting and molding processes utilize vibratory force to separate a casting or part from its mold and concomitant media. In many prior art systems, foundries utilize vibratory shakeout devices to mechanically separate sand or other surrounding media used in the casting process from the casting itself.
In operation, prior art vibratory shakeout devices have attempted to control the time a casting is retained in its mold by changing the elevation of one end of the shakeout to change the angle of inclination of the conveyor trough. Longer casting retention times are typically required for more complete media removal whereas short retention times are desirable for more fragile castings since a shorter retention time typically requires that less vibratory force is imparted through the conveyor trough to the fragile casting. Increasing the angle of inclination of a shakeout typically increases the retention time of a casting in the mold and, conversely, decreasing shakeout inclination usually decreases mold retention time.
Many prior art shakeout systems utilizing angle of inclination type control systems are relatively unreliable since they typically employ complex mechanical systems such as air bellows or hydraulic cylinders to elevate an end of the shakeout. These mechanical systems are inherently unreliable, particularly in the harsh industrial environment of a foundry or other molding facility. Furthermore, many prior art systems offer only a limited range of process control since the angle of inclination can only be raised a few degrees before the ability to convey the casting forward along the conveyor trough ceases unless a tremendous amount of vibratory force is applied. Additionally, variations in casting speed are difficult to effect with these prior art systems.
The present invention provides a system and method for controlling the retention time of an article on a vibratory conveyor that modifies the angle of the vibratory force imparted to the conveyor as a function of the desired retention time or alternatively, as a function of article position on the conveyor or another sensed variable that is indicative of article progress. The present invention provides an electronically adjustable system for controlling conveyor retention time that permits an article being conveyed to be monitored such that a desired result is achieved prior to the article being discharged from said conveyor. For example, the present invention may be employed to monitor casting retention in a mold and adjust or modify that retention time based on a desired retention time or alternatively based on other sensed variables such as article position, relative amount of media removal, or both.
The invention comprises a vibratory shakeout conveyor that may utilize an electronic control system to modify the relative angle of the vibratory force applied to the conveying surface responsive to a desired retention time, either as input by an operator or responsive to a sensed variable such as casting position or media removal. A plurality of sensors may be employed, both to monitor and adjust the resultant angle of vibration and also to monitor the progress of the article being conveyed and its condition or status relative to a desired status prior to advancing the article.
The present invention may incorporate at least one electric motor that is capable of being electronically controlled, for example by a variable frequency drive, responsive to an resultant angle of vibration or speed input supplied thereto. The motor speed is readily adjusted to modify the relative speed of a rotating shaft or shafts, thereby changing the resultant angle of vibratory force being applied to said conveyor. Other objects, features, and advantages of the present invention will become apparent upon an examination of the detailed description of the preferred embodiment taken in conjunction with the drawing Figures.
Referring now to the drawing Figures, and in accordance with a preferred constructed embodiment of the invention, a system 10 and method for controlling the retention time of an article comprises a vibratory conveyor 20 including a trough or conveying surface 21 which is mounted on a stationary base 22 by a plurality of isolating springs 24 or equivalent resilient mounting means. A plurality of shafts 30, 32, and 34 are mounted for rotational motion within a frame 40. Each shaft further includes at least one eccentric weight 36 positioned at a point between the ends thereof that rotates with its respective shaft. In one embodiment of the present invention an exemplary system 10 may employ a plurality of eccentric weights 36 centrally positioned on shaft 32 while the outboard shafts 30 and 34 may employ just a single eccentric weight 36. Each shaft further includes a pulley 38 mounted thereon that is driven by a belt 42 that is in turn driven by a pair of motors 44 and 46 respectively, each having associated pulleys 48 secured to their output shafts.
In an exemplary embodiment of the present invention as shown in
The system 10 thus far described comprises an eccentric weight vibratory conveyor 20 capable of altering the direction of the resultant force acting on conveyor 20 due to the centrifugal forces imparted thereto by the rotating eccentric weights 36. The direction of the resultant force acting on conveyor 20 is dependent upon the relative phase angle between the positions of the rotating eccentric weights 36. Accordingly, by varying that relative position or relative phase angle between the shafts and therefore the weights 36, the direction or angle of resultant vibratory force acting on conveyor 20 is varied so that the conveying rate and direction of material placed on conveyor 20 can be altered.
The system 10 may further comprise a plurality of proximity sensors or switches 60 positioned proximate shafts 32 and 34 capable of sensing the position of the respective shafts by sensing a flag or other detectable element located thereon, as is well known to one of ordinary skill in the art. Sensors 60 provide an output 62 responsive to a sensed shaft position that is operatively connected to a controller 70. Controller 70 may comprise a conventional microcontroller having a processor, an associated data memory and a plurality of inputs and outputs that may be operatively coupled to external devices as discussed further herein below.
Controller 70 calculates an actual value of relative phase angle Ø1 between shafts 32 and 34 by comparing the shaft position signal inputs 62. A manually operated user input 72, which may comprise a known in the art potentiometer, thumbwheel switch, or alternatively a numerical keypad having an output representative of a user's selection, may be adjusted to provide a desired speed and direction signal to controller 70. It should be noted that user input 72 may be either a desired relative phase angle setting or alternatively a speed and direction setting. In the case of the latter, controller 70 may be suitably programmed to mathematically convert a desired speed and direction setting supplied by user input 72 to a desired phase angle either by use of a look up table or a suitable mathematical formula, as is well known to one of ordinary skill in the art.
The controller 70 provides an output signal 73 representative of a desired motor 46 speed to a variable frequency drive 80 or equivalent electronic motor controller, thereby altering the speed of motor 46 to change the relative phase angle between shafts 30, 34, and shaft 32. The signal 73 sent to variable frequency drive 80 is continuously adjusted by controller 70 to maintain a desired relative phase angle thereby advancing an item positioned on vibratory conveyor 20 as desired.
In an alternative embodiment of the invention, a plurality of photo-eyes, motion detection, or infra-red sensors 74 or equivalent sensors are positioned at a plurality of locations along vibratory conveyor 20 to sense the progress and position of an article placed thereon. The sensors 74 include associated outputs 76 operatively connected to a plurality of inputs of controller 70. Sensors 74 are positioned at various points along the path of articles being conveyed to monitor the advancement of the articles or alternatively the amount of media breakdown which has occurred in a mold containing a casting, which in turn may be used to vary relative phase angle Ø and alter conveying speed and/or direction as discussed in detail herein below.
Referring to drawing
At that predetermined position depicted in
The requisite changes to the resultant angle of vibration Ø applied to conveyor 20 may be effected by a plurality of embodiments of the present invention. In one exemplary embodiment, a first sensor 74 is a motion detection sensor, for example a commercially available PIR sensor or its equivalent that is capable of detecting motion at a point or area in space and producing an output responsive thereto, coupled to an input of controller 70. In its initial state, controller 70 advances casting 1 along conveyor 20 at predetermined angle Ø1 (and thus at a predetermined speed) until the casting reaches a point where sensor 74 detects the presence of casting 1 and sends an output to controller 70. Once controller 70 senses the output from sensor 74 indicating the presence of casting 1 controller 70 then sends a new speed signal 73 to variable frequency drive 80 to alter the speed of motor 46 and increase the resultant angle of vibration to Ø2 to stop the advancement of casting 1 and facilitate the breakdown of media 2.
The controller 70 may, in one embodiment of the present invention, simply set the resultant angle of vibration to Ø2 for a predetermined time period selected to permit media 2 to substantially breakdown, whereupon controller 70 then automatically provides a new speed signal 73 to variable frequency drive 80 to change the resultant angle of vibration to Ø3 to discharge casting 1 from conveyor 20.
In a yet further embodiment of the present invention, a second sensor 74, for example a photo-eye or its equivalent is positioned at a point proximate the area of conveyor 20 where casting 1 stops advancing (at resultant angle of vibration Ø2) to sense when media 2 has substantially broken down. Stated another way, second sensor 74 is capable of detecting the absence of media 2 proximate casting 1 and sends a signal to controller 70 indicating that casting 1 is ready to be discharged from conveyor 20. Alternatively, second sensor 74 may comprises one of a plurality of commercially available digital cameras that are capable of detecting surface voids or imperfections in a viewing area. In this embodiment of the invention, the digital camera may readily determine the absence (or presence) of media 2 in a given are when casting 1 has reached a predetermined positioned and send an output indicative of a predetermined media breakdown to controller 70.
In an additional embodiment of the present invention controller 70 operates vibratory conveyor 20 in a pulse mode wherein once casting 1 enters conveyor 20 the resultant angle of vibration Ø is alternately increased and decreased to impart a greater, then lesser vibration to casting 1. In this fashion, articles placed on conveyor 20 are advanced in a pulsing fashion, which further facilitates the breakdown of media 2. Pulse mode operation may further be enhanced by utilizing a plurality of sensors 74 to determine the presence or absence of media 2 around casting 1 at a predetermined point along conveyor 20. When casting 1 reaches the predetermined point, if media 2 is not sufficiently removed therefrom, as detected by a photo-eye or infrared sensor 74, controller 70 may send a speed signal 73 to variable frequency drive 80 to increase the resultant angle of vibration Ø such that casting 1 reverses direction on conveyor 20 for a predetermined time or, alternatively, until casting 1 is sensed by a second sensor 74 at a second point along conveyor 20. At this point controller 70 once again initiates pulse mode operation to advance casting 1 while removing media 2 therefrom. This process may reiterate itself until media 2 has been substantially removed from casting 1 whereupon the casting is advanced out of conveyor 20.
While the present invention has been shown and described herein in what are considered to be the preferred embodiments thereof, illustrating the results and advantages over the prior art obtained through the present invention, the invention is not limited to those specific embodiments. Thus, the forms of the invention shown and described herein are to be taken as illustrative only and other embodiments may be selected without departing from the scope of the present invention, as set forth in the claims appended hereto.
This application for patent is a divisional application of, and claims the benefit of co-pending U.S. patent application Ser. No. 11/278,606 filed Apr. 4, 2006, and entitled “System and Method for Controlling Casting Shakeout Retention”.
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| Number | Date | Country | |
|---|---|---|---|
| Parent | 11278606 | Apr 2006 | US |
| Child | 12759354 | US |
