GB2070281A

GB2070281A - Control of coating apparatus

Info

Publication number: GB2070281A
Application number: GB8102788A
Authority: GB
Original assignee: Champion Spark Plug Co
Current assignee: Federal Mogul Ignition Co
Priority date: 1980-02-27
Filing date: 1981-01-30
Publication date: 1981-09-03
Also published as: IT8147706A0; IT1170683B; FR2476507A1; JPS56126462A; GB2070281B; DE3102779A1

Abstract

A coating pattern matrix for each different type of workpiece is stored in the memory of a microprocessor master controller. The master controller also includes a first-in, first-out memory storing style data identifying each successive workpiece. As a workpiece enters a coating station along the conveyor, the style data for such workpiece identifies and causes a transfer of the coating pattern data for such workpiece to a controller for a reciprocating coater at the coating station.

Description

SPECIFICATION Control for reciprocating sprayers BACKGROUND OF THE INVENTION This invention relates to paint spray systems and more particularly to an improved paint spray system in which a series of workpieces are conveyed horizontally past a vertically reciprocating spray gun.

In many manufacturing environments, it is desirable to have a system capable of spray painting workpieces as they move on a conveyor system. In one type of system, one or more spray guns are mounted on a carriage which is reciprocated vertically or in a direction transverse to the direction in which the workpieces are conveyed. As the reciprocating spray gun sweeps across a portion of the surface of the workpiece, the spray gun is turned on to apply a coating to the workpiece.

Various types of controls have been used in the past for reciprocating spray painting systems. United States Patents 3,593,308 and 3,646,521 are directed to control circuits for reciprocating sprayers. The workpieces are conveyed past a vertical array of photocell detectors before they enter the spray station.

The photocell detectors generate data on the vertical and horizontal dimensions of each conveyed workpiece. The workpiece dimensional data is digitized and stored in a memory matrix for controlling the reciprocating sprayer as the workpiece is conveyed through the spray station. United States Patent 3,989,003 is directed to a modified control for a reciprocating sprayer positioned next to a horizontal workpiece conveyor. As a workpiece enters a job input station, an operator enters into the system data on the position, the style and the desired color for the workpiece. This data is stored in a memory until the object reaches the spray station. At this time, the job data information entered by the operator is compared with pre-programmed information.When a match occurs, the preprogrammed information causes the spray guns in each spray station to move to the proper position and then actuates the guns for spraying the workpiece as it is conveyed past the sprayer.

SUMMARY OF THE INVENTION According to the present invention, an improved system is provided for controlling a plurality of reciprocating coaters such as paint sprayers to sequentially coat workpieces moving on a conveyor. Initially, a workpiece identification code and a color code-are entered into the system either automatically or manually by an operator while the workpiece is upstream from the first spray station. The identification and color data are entered into a queue in a first-in, first-out memory. The system includes a computer provided with a main memory storing a lumber of XY matrixes representing the horizontal and vertical coating patterns of a number of different parts. As each part is conveyed into the spray station, the identification data for the part is read out of the queue in the first-in, first-out memory.This data causes a transfer of the XY matrix for the identified part to a temporary memory in a spray station control associated with the first reciprocating sprayer along the conveyor. The spray station control may be a separate unit located near the reciprocator or it may be part of the main control. The workpiece then is coated as it passes the first reciprocating sprayer. The XY matrix for the particular workpiece subsequently is transferred from the microprocessor to the spray station control for each subsequent reciprocating sprayer along the conveyor as the workpiece is conveyed into each successive spray station. Through this arrangement, a workpiece is automatically coated with several layers as it is conveyed through the successive spray stations.Or, a different pattern for coating different portions of the workpiece can be transferred from the main memory to the spray station control and memory for each successive reciprocator. Several different workpieces may be coated at the same time by the different reciprocating sprayers located in the different spray stations along the conveyor. The individual sprayers need not be synchronized with each other since each reciprocating sprayer is operated by a spray station control which temporarily stores an XY spray pattern matrix for the workpiece which the sprayer is currently coating. If desired, the individual sprayers may be adapted to automatically change color between successive workpieces and to automatically purge all of the previous color paint from the system before initiating spraying with a new color.

Accordingly, it is an object of the invention to provide an improved control for reciprocating sprayers located adjacent a workpiece conveyor.

Another object of the invention is to provide an improved system for coating a series of different workpieces as they are sequentially conveyed past a plurality of reciprocating sprayers.

Other objects and advantages of the invention will become apparent from the following detailed description, with reference being made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary side elevational view of a vehicle body being conveyed past a reciprocating sprayer; Figure 2 is an illustration of an XY matrix for the spray pattern for the vehicle body shown in Fig. 1; and Figure 3 is a schematic block diagram of a control for reciprocating sprayers constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODI MENTS Turning now to the drawings and particularly to Fig. 1, a spray station 10 is illustrated for coating a workpiece 11, such as an automobile body, as it moves on a conveyor 1 2.

The spray station 10 is provided with a reciprocating- sprayer 1 3 which coats the workpiece 11 as it moves on the conveyor 1 2. The reciprocating sprayer 1 3 may be of any type well known in the prior art and may include a carriage 14 on which a plurality of paint spray guns 1 5 are mounted. Or, other types of coaters such as powder coaters may be mounted on the carriage 14 in place of the spray guns 1 5. A suitable drive system (not shown) is provided for reciprocating the carriage 1 4 in a vertical direction, as illustrated by the arrow 1 6. At the same time the carriage 14 is reciprocated, the workpiece 11 is conveyed in a horizontal direction past the spray guns 15, as illustrated by the arrow 1 7.

After the previous workpiece is coated and prior to the workpiece 11 reaching the reciprocating sprayer 13, and XY matrix corresponding to the areas of the workpiece 11 to be coated is transferred to a spray station control and memory 1 8. The spray station control and memory 18, which also is supplied with current positional data for the workpiece 11 and if desired, also for the reciprocator carriage 14, selectively turns on and off the individual spray guns 1 5 as the workpiece 11 is moved past the sprayer 1 3 to uniformly coat the workpiece 11 in accordance with the XY matrix. The individual spray guns 1 5 are turned on only as long as the spray guns are sweeping across a surface portion of the workpiece 11 to be coated.In the case of an auto body, for example, the individual spray guns 1 5 can be turned off as they sweep across voids in the workpiece 11 such as a window opening 1 9. Of course, the turning on and off of the guns as they sweep across voids in the workpiece is subject to the response time required to turn the guns on and off. Some coaters, such as powder coaters, have a relatively long response time as compared to liquid paint spray guns.

Fig. 2 illustrates an exemplary XY matrix 20 for controlling the reciprocating sprayer 1 3 to coat the exemplary workpiece 11. The matrix 20 is in the form of a grid divided into a preselected number of vertical and horizontal areas. The number of vertical and horizontal areas is determined by the memory capacity of the spray station control memory 1 8 and also of a related master controller which is discussed in detail below. The matrix 20, for example, may have a resolution of 1 28 vertical spaces or rows and of 256 horizontal spaces or columns. This matrix may be adapted to cover any desired resolution. For example, if the memory matrix 20 is designed to cover an 8 foot by 20 foot pattern, there will be 3/4 inch vertical resolution and 15/16 inch horizontal resolution in the matrix 20.The matrix 20 provides information as to when the individual spray guns 1 5 should be turned on and off as the workpiece 11 is conveyed past the reciprocating sprayer 1 3. A data bit is stored for each region of the matrix 20 which corresponds with a region of the workpiece 11 to be coated. In addition, a data bit may be stored in portions of the XY matrix 20 immediately leading and lagging the work-1 piece 11 so as to provide a uniform coating on the workpiece 11 as it is conveyed past the reciprocating sprayer 1 3.

Turning now to Fig. 3, a detailed block diagram is shown for a control system 25 in accordance with the present invention for op- ,, erating a plurality of reciprocating sprayers 1 3a, 1 3b, 1 3c through 1 3i. The plurality of reciprocating sprayers 1 3a-1 3i are located at individual spray stations 10a-10i, respectively, spaced along the conveyor 1 2 for sequentially coating a series of conveyed workpieces. Each reciprocating sprayer 1 3a-1 3i may be provided with a vertical encoder 26a-26i, respectively, which generates a signal indicative of the current vertical position of the corresponding reciprocating sprayer 1 3a-1 3i. Each vertical encoder signal is applied to the associated spray station control and memories 18a-18i.The spray station control and memories 1 8a-1 8i for the spray stations 10a-10i are each either connected to or integral with a master controller 27 which preferably is a microprocessor, such a a model TMS9900 CPU manufactured and sold by Texas Instrument Company. However, it should be appreciated that the functions of the master controller 27 and the individual spray station controls and memories 1 8a-1 8i also may be performed by a general purpose digital computer on either a full or a time shared basis.

The master controller 27 includes memory space for storing XY matrixes, such as the matrix 20 illustrated in Fig. 2, for the spray pattern for each of a plurality of different workpieces which are to be coated by the reciprocating sprayer 1 3a-1 3i. The XY matrixes are stored in a read and write memory and may be entered and/or modified through a keyboard (not shown) incorporated in a program station and CRT display 28. A manual schedule station 29 also is illustrated connected to the master controller 27. Style data indentifying each successive workpiece on the conveyor 12 is entered through the schedule station 29 along with data when needed, identifying the color which each successive workpiece is to be coated. The color data may be entered for each workpiece or only when there is a color change.The schedule data may be entered at the station 29 either manually by means of a keyboard (not shown) or through other means such as a card reader which reads the data from a punch card for each workpiece. Or, the manual schedule station 29 may be replaced with an automatic identification system which may include photoelectric devices for viewing each successive workpiece on the conveyor 1 2 and circuitry responsive to the unique physical geometry of each workpiece for generating digital style data identifying such workpiece.

Automatic workpiece identification systems of this type are known in the prior art. The style and possibly color data for each successive workpiece, whether entered through the manual schedule station 29 or through an automatic scheduling station, are stored in a firstin, first-out memory within the master controller 27. This type of memory will permit reading the stored data in the same sequence in which the corresponding workpieces are conveyed to the spray stations.

The master controller 27 also has an input from a sensor 30 positioned adjacent the conveyor 1 2. The sensor 30 may consist of an optical sensor, such as a photo detector, which generates an output when each successive workpiece is conveyed to a predetermined location wherein a light beam is interrupted. Or, the sensor 30 may consist of a mechanical switch which is tripped by each successive workpiece or by a hanger which supports each successive workpiece on the conveyor 1 2 as each workpiece is conveyed past a predetermined location. Finally, the master controller 27 has an input from an encoder 31 which is connected to the conveyor 12. The encoder 31 generates a signal each time the conveyor 1 2 advances a predetermined small increment.By counting output pulses from the conveyor encoder 31 after a workpiece passes the predetermined location of the sensor 30, the exact position of the workpiece is accurately tracked as the workpiece is conveyed sequentially past the spray stations 1 Oa- 1 0i.

Once a workpiece passes the sensor 30, the master controller 27 continues to track the location of such workpiece as it is conveyed sequentially past the spray stations 10a-10i.

When the workpiece reaches the first spray station 1 Oa, the style and color data for such workpiece is read from the first-in, first-out memory in the master controller 27. The master controller 27 then locates the XY matrix for the workpiece in response to the style data identifying the workpiece and transfers the XY matrix and the color data to the spray station control and memory 1 8a for the spray station 1 Oa. The spray station control and memory 1 spa, which also may consist of a separate integrated circuit microprocessor or may be incorporated with the master controller into a single computer, stores the transferred data in a temporary memory.Before a workpiece enters a spray., station and, preferably, immediately after the last workpiece left such spray station, the master controller 27 also compares the color data for such workpiece with color data for the previous workpiece coated at such spray station. If there is a change in color, the master controller 27 causes the spray station control and memory to apply a predetermined timed sequence of signals on outputs 32a to operate color select solenoids, solvent solenoids and purge air solenoids for purging all paint from the spray guns mounted on the reciprocating sprayer and from the connected paint lines and introduces the new color.The purging cycle and color change operation is in accordance to a preset cycle or program stored in the master controller 27, as exemplified by the cycle described in United States Patent 3,674,205, the disclosure of which is incorporated herein.

The color purging cycle takes place between workpieces. If desired, changes in purge cycle times may be manually entered through the program station 28.

The painting program consisting of the XY matrix and color data for a workpiece are transferred to the first spray station control and memory 1 8a when the workpiece to be coated in accordance with such data is a distance from the reciprocating sprayer 13a.

The output of the conveyor encoder 31 which is applied to the master controller 27 also is applied either directly or indirectly through the master controller 27 to each of the spray station controls and memories 1 8a-1 8i. The spray station control and memory 1 8a is provided with a counter which counts pulses from the encoder 31 from the point of time when program data is transferred from the master controller 27 to the spray station controller and memory 18a.This data identifies the exact location of the workpiece as it passes through the spray station 1 0a. Or, a sensor or a limit switch may be located to indicate when the workpiece is at a predetermined location in the spray station 10a. Once this sensor or limit switch is tripped, pulses from the encoder 31 are counted to track the position of the workpiece as it moves through the spray station 1 Oa.

In one embodiment, the workpiece position pulses from the conveyor encoder 31 are used in the spray station control and memory 1 8a to sequentially shift each vertical column in the XV spray matrix to a register as the corresponding region of the workpiece passes the spray guns 15a. In other words, if each column of data corresponds to 15/16 inch of horizontal resolution of the workpiece, then the next column of the XV matrix is shifted to the register each time the workpiece advances 1 5/1 6 inch. As the workpiece is conveyed past the reciprocating sprayer 13a, the output from the vertical encoder 26a applied to the spray station control and memory 1 8a identi fies the vertical position of each of the spray guns 1 5a on the reciprocating sprayer 1 3a.

The data bits in the locations in the vertical column of data currently stored in the register corresponding to the vertical positions of the individual spray guns 1 spa on the reciprocator 1 3a control the oututs 32a from the spray station control and memory 1 8a to selectively turn on and off each of the spray guns 1 spa.

As the spray guns 1 spa continue to reciprocate in a vertical direction, the columns of data in the XY matrix for the workpiece are sequentially shifted to the register in synchronism with the conveyed workpiece. Once the workpiece moves past the spray guns 1 5a, the entire matrix will have been shifted to the register and at this time the memory within the spray station control and memory 1 8a will be clear.

As the workpiece then is conveyed to the next spray station lOb, either the same XY matrix or a different XV matrix for a different portion of the workpiece is transferred from the master controller 27 to the spray station control and memory 1 8b which controls the spray guns 1 sub on the reciprocator 1 3b. This is repeated at each of the following spray stations 1 Oc through 1 Gi. It should be noted that the matrixes transferred to each successive spray station control and memories 1 8a-1 8i may differ for a workpiece if different workpiece areas such as left side, top, right side, etc., are coated at the different spray stations.

In another preferred embodiment of the spray station control and memories 18a-18i, the shift register is omitted. The XV matrix for a workpiece is stored in a memory so long as such workpiece is at the spray station. As the workpiece is conveyed past the spray guns, pointers for each spray gun on a reciprocator look at the memory addresses corresponding to the current position of the spray guns relative to the workpiece. In this embodiment, the spray station control may be integral with the master controller and the pointer may address memory locations corresponding to current coater positions on the XV matrix directly in the main read and write memory in the master controller.

It should be noted that each of the reciprocating sprayers 1 3a through 1 3i are controlled independently of the other reciprocating sprayers. In view of this, the spacing between the reciprocating sprayers 1 3a through 1 3i is not critical so each individual reciprncating sprayer 1 3a through 1 3i need not be synchronized with the others of the reciprocating sprayers 1 3a through 1 3i. Since each of the reciprocating sprayers 1 3a through 1 3i is controlled independently of the others, it should be appreciated that different types of workpieces may be coated at the same time by each of the reciprocating sprayers 1 3a-1 3i.Furthermore, the workpieces may be provided with random spacings on the conveyor 1 2 since the master controller 27 keeps track of the location of each workpiece on the conveyor 1 2 with respect to the individual spray stations 10a-10i. Or, in the alternative, a limit switch may be provided at each spray station 1 0a through 1 0i. As a workpiece enters one of the spray stations 1 Oa through 1 0i, the limit switch signals the master controller 27 to select the XV matrix for such workpiece for controlling that spray station.

It will be appreciated that various changes and modifications may be made in the above described embodiments of a control for reciprocating sprayers without departing from the spirit and the scope of the following claims. It also will be appreciated that the invention is applicable to different types of coaters includ- ing liquid spray guns and powder coaters.

Claims

1. Apparatus for coating a series of different workpieces moving in a predetermined direction on a conveyor comprising a coating applicator, means for reciprocating said coating applicator in a direction substantially perpendicular to said predetermined direction, first memory means storing coating pattern data for each different workpiece to be coated, second memory means for temporarily storing the coating pattern data for a workpiece currently being coated by said coating applicator, means for generating position data corresponding to the current position of a workpiece, control means responsive to such position data and such coating pattern data in said temporary memory for selectively turning said coating applicator on and off to coat a workpiece in accordance with the coating pattern data for such workpiece, third memory means storing in sequence style data identifying each workpiece in the series, and means responsive to such sequence data in said third memory means for reading the coating pattern data for a workpiece from said first memory means and storing such read coating pattern data in said second memory means as such workpiece is conveyed to said coating applicator.

2. Apparatus for coating a series of differ- - ent workpieces moving on a conveyor, as set forth in claim 1, and further including a plurality of said coating applicators spaced along the conveyor, a like plurality of said second memory means and of said control means with a separate second memory means and a separate control means associated with each coating applications, wherein said means for generating position data includes means for generating position data includes means for generating position data of each of said coating applicators, and wherein said means responsive to such sequence data in said third memory means includes means for reading the coating pattern data for a workpiece from said first memory means and for sequentially storing such read data in each of said second memory means associated with each succes sive coating applicator along the conveyor as such workpiece is conveyed to each successive coating applicator, whereby such workpiece is successively coated as it is conveyed past each successive coating applicator.

3. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claim 1, and further including a plurality of said coating applicators spaced along the conveyor, a like plurality of said second memory means and of said control means with a separate second memory means and a separate control means asosociated with each coating applicator, wherein said means for generating position data includes means for generating position data for each workpiece being coated by a coating applicator and for each coating applicator, and wherein said means responsive to such sequence data in said third memory means includes means for reading the coating pattern data for each workpiece from said first memory means as such workpiece is conveyed to a coating applicator and for storing such read coating pattern data in the second memory means associated with such coating applicator, whereby each workpiece is successively coated as it is conveyed past each successive coating applicator.

4. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claims 1, 2 or 3, wherein said third memory means is a first-in, first-out memory.

5. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claims 1, 2 or 3, and further including means for modifying coating pattern data stored in said first memory means.

6. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claims 1, 2 or 3, and further including means for generating position data corresponding to the current position of said coating applicator, and wherein said control means responsive to position data is responsive to both workpiece and coating applicator position data.

7. Apparatus for coating a series of different workpieces moving in a predetermined direction on a conveyor comprising a coating applicator, means for reciprocating said coating applicator, means for reciprocating said coating applicator in a direction substantially perpendicular to said predetermined direction, first memory means storing coating pattern data for each different workpiece to be coated, means for generating position data corresponding to the current position of a workpiece on the conveyor, second memory means storing in sequence style data identifying each workpiece in the series, and control means responsive to workpiece position data, the style data in said second memory and the coating pattern data in said first memory for selectively turning said coating applicator on and off to coat a workpiece as it is conveyed past said coating applicator in accordance with the stored coating pattern data for such workpiece.

8. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claim 7, wherein said control means includes a third memory, means responsive to style data in said second memory for reading the coating pattern data for the next workpiece to be coated and storing such read coating pattern data in said third memory, and means responsive to position data on such next workpiece and to coating pattern data in said third memory for turning said coating applicator on and off to coat such next workpiece as it is conveyed past said coating applicator.

9. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claim 8, and including a plurality of said coating applicators simultaneously reciprocated by said reciprocating means, and wherein said means responsive to position data on such next workpiece to coating pattern data in third memory selectively turns each of said coating applicators on and off to coat such next workpiece as it is conveyed past said coating applicator.

10. Apparatus for coating a series of different workpieces moving on a conveyor, as set forth in claim 9, and further including means for generating position data corresponding to the positions of said coating applicator, and wherein said means responsive to position data on such next workpiece is responsive to both workpiece and coating applicator position data.

11. Apparatus for coating a series of different workpieces, comprising a coating applicator, a first memory containing coating pattern data for the different workpieces, a second memory containing style data for the different workpieces, means for providing an indication of the position of a respective workpiece relative to the applicator, and control means arranged to respond to the position indicating means and to the style data for the respective workpiece from the second memory for controlling the applicator so as to coat the respective workpiece in accordance with the coating pattern data for the respective workpiece from the first memory.

1 2. Coating apparatus substantially as herein particularly described with reference to and as illustrated in the accompanying drawings.