US 3724415 A
A spray gun for coating surfaces of a succession of articles of different shapes and sizes has the position of emission of liquid therefrom maintained substantially at a predetermined distance from the surface being sprayed by a variable profile cam the profile of which is automatically varied by adjusting means operable under control of control means which in turn is controlled by sensing devices located along the path of the article and which are arranged to sense the shape and size of the article.
Description (OCR text may contain errors)
O United States Patent 1191 1111 3,724,415 Knight 1451 Apr. 3, 1973  CONTROLLING SPRAY GUNS 2,321,982 6/1943 Brackett ..118/323  Inventor: Howard Richard James Knight, 52:; Hampton, England 3,594,211 7/1971 Drum ..117/107.3  Assignee: Carrier Engineering Company Limited, London England Primary Examuter-Mervm Ste1r 1 I Assistant ExaminerLeo Mlllsteln  Flled: 1970 Attorney-Snyder and Butrum  A 1. No.: 67 868 pp 57 ABSTRACT  Foreign Application Priority Data spray gun for coating surfaces of a success'ionof articles of different shapes and s1zes has the pos1t1on of Sept-3,1969 Great 1311mm emission of liquid therefrom maintained substantially at a predetermined distance from the surface being U.S. Cl prayed a variable profile cam the profile of 113/323 is automatically varied by adjusting means operable  Int. Cl. ..B05c 11/00, B05b 3/00 under control of control means which in turn is conl Field 0f Search trolled by sensing devices located along the path of 117/1053, DIG 2 the article and which are arranged to sense the shape and size of the article.  References Cited 10 Claims, 9 Drawing Figures UNITED STATES PATENTS 3,255,037 6/1966 Knight et al ..118/2 Inventor PATENTEUAPM I973 SHEET 3 OF 4 Inventor CONTROLLING SPRAY GUNS BACKGROUND OF THE INVENTION gun, and it may be used with particular advantage in the spray coating of automobile bodies. I
In the mass production of automobile bodies it is frequently the case that bodies of different styles follow one another through the spray coating apparatus and, furthermore, as each body passes through the spraying apparatus it generally presents a succession of surfaces of different shapes and sizes to be sprayed. In addition to variations in the general outlines of the bodies there are variations in the contours of the bodies which it is generally necessary to follow in order to avoid unacceptable variations in the finish and thickness of the coatings applied.
' transversely of the path of travel of the bodies, the
tracks having associated cam tracks following the body surfaces facing them so that the guns as they are reciprocated follow the contours of the bodies.
Such known kinds of paint spraying apparatus have the disadvantage that they must be set up with the appropriate cams for each form of body being coated, and they are not therefore capable of painting a succession of bodies of differing contours.
The present invention relies upon the conception that, because the distance from the contour of a body to the middle of a cord is not as a rule critical, the contour of a body cam can be split up into separate chords joined together by generous curves.
SUMMARY According to the present invention there is provided an apparatus for coating surfaces of a succession of articles of different shapes and sizes by a spray gun reciprocable along a path in a first plane during movement of the surfaces past the gun along a path in a second plane at right angles to said first plane, comprising sensing devices located along the path of the articles and operable to sense the shape and size of the article, a variable profile cam operable to control the movements of the gun in said first plane, cam profile adjusting means, and control means connected with said sensing devices and said cam profile adjusting means and operable to actuate the cam profile adjusting means to adjust the profile of the cam according to the form of the surface to be sprayed thereby during reciprocation of the spray gun to maintain the position of emission of liquid from the spray gun substantially at a predetermined distance from the surface being sprayed.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 diagrammatically shows a side view of an automobile body, a spray coating apparatus and elements of a body form detecting device,
FIG. 2 shows a side view of an adjustable cam,
FIG. 3 shows an enlarged cross section on the line 3-3 of FIG. 2,
FIGS. 4 and 5 show side views of a further embodiment of adjustable cam in different operating positions thereof,
FIG. 6 shows in block schematic form a circuit arrangement and adjusting means for adjusting the shape ofa cam as shown in FIG. 3, and
FIGS. 7, 8 and 9 show diagrammatic representations of a longitudinal section through a spray gun guiding arrangement in different operating positions thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown an automobile body 1 supported by a hanger or truck (not shown). The arrangement is such that bodies of different shape and size following consecutively may be handled.
The spraying apparatus includes a structure having two vertically disposed side units 2, only one olwhich is shown, spaced apart one on either side of the path of travel of the bodies, and a horizontally disposed unit 3, above the path of travel of the bodies, for side spray guns 4 and top spray guns 5. The spray guns 4 and 5 are reciprocable along their units in first planes at right angles to a plane along which move the body surfaces which the spray guns are arranged to coat. The length of traverse of the side spray guns 4 is indicated by a slot 8 in the casing of the vertical unit 2.
A plurality of photoelectric devices 9, 10, 11, 12 and 13, positioned local to thespray gun units, or in prior positions, that is before the spray booth in which spray,- ing is effected, are arranged to detect the presence of a body or a particular part of a body and to provide signals to a programming arrangement which controls the extent both of the movement of the spray guns along their respective units and the periods of time during which spraying takes place, as described in US. Pat. specification No. 3,255,037, Knight et al.
It is, of course, necessary for there to be some movement of the guns in the planes referred to, both towards and away from a body being sprayed, in order to follow the curve of the body and ensure an even coating. The control of this movement of the guns is generally by means of fixed cams and where a succession of bodies of different shape and size as seen from the side view, but with sides and tops presenting curves of similar shape as seen from the end view, is employed such an arrangement is quite satisfactory. However, when successive bodies having cross-sectional profiles which differ considerably are employed or when the crosssectional profile varies considerably over the length of a body, such an arrangement employing a compromise shape of cam is not satisfactory.
Referring to FIG. 2 there will now be described a variable profile cam in its simplest form which is particularly suitable for use with apparatus of the kind described with reference to FIG. 1 in controlling the movement of spray guns so that they may follow the profiles of different bodies with the position of emission of liquid therefrom maintained at a substantially predetermined distance from the surface being sprayed. In FIG. 2 there is shown a first cam member 15 formed from a U-section channel member having two straight portions 16 and 17 joined by a curved portion 18. The upper end 20 of the member 15 is movable by means of a piston rod 21 from a pneumatically operated double acting cylinder 22. The lower end 23 of the member 15 is attached to a bracket 24 which is pivoted about a fixed pivot 25 so that the arm 15 can be rotated about the pivot 25 by the action of the cylinder 22 into either one of two positions, namely the position in which it is shown and the position indicated by the dotted line 15a.
There is also pivoted about the pivot 25, by means of a bracket 26, a second cam member 27 formed as a straight member having a U-section channel.
The lower end of the member 27 is attached to the piston rod 28 of a double acting cylinder 30, which in turn is coupled to the piston of a double acting cylinder 31, whereby the cam member 27 may be moved by the action of the cylinders from the position shown into either of the positions indicated by the dotted lines 27a and 27b. At the bases of the U-section channels 15 and 27 there is a cam profile-forming strip consisting of a flexible steel strip 32 which extends lengthwise of the channels 15, 27 and is maintained in tension by a coiled tension spring, indicated at 33. The strip 32 provides a cam profile within the members 15 and 27 and continues as a curve between the ends of these members at the brackets 24 and 26.
The cross-section shown in FIG. 3 makes clear the position of the strip 32 within the member 15.
Referring to FIGS. 4 and there are shown first, second, and third cam members 40, 41 and 42 formed from straight lengths of U-section channels.
The second member 41 is coupled by arms 44 and 46 at its opposite ends to the ends of an arm 49 to form a unitary structure. The arms 44, 46 extend in opposite directions at right angles to the second cam member 41. The rocking arm 49 is pivoted about a fixed pivot point 50 and the opposite-ends of the rocking arm 49 carry pivots 45 and 48 about which brackets 43 and 47, attached to the ends of the first and third cam members 40 and 42 respectively, may pivot. The second cam member 41 may be positioned by rotation of the rocking arm 49 about the pivot 50 either manually, by means of a pneumatically operated cylinder 51, or by any other rotatable means, acting on the rocking arm 49. Furthermore the unitary structure formed by the rocking arm 49, the arms 44 and 46 and the second cam member 41 may, in a modified embodiment, be moved vertically by arranging the pivot 50 in a slot and acting on the structure either by means of a remotely controlled pneumatically operated cylinder (not shown) or manually. In a similar manner to the arrangement of FIG. 2, the end 52 of the third cam member 42 is connected to the piston rod of a cylinder 53 which in turn is coupled to the piston rod of a cylinder 54 and the end 55 of the first cam member 40 is connected to the piston rod of a cylinder 56. There is also a flexible steel strip 57 passing along the bottom of the U-section cam members 40, 41 and 42 and providing a cam profile within and between the members. The strip 57 is maintained under tension by two coiled tension springs 58 and 59 at its opposite ends.
In addition to the straight cam profile which may be provided by the arrangement as shown in FIG. 5 and the arrangement as shown in FIG. 4, various possible other combinations of the positions of the first and third cam members 40 and 42 are indicated at 40a, 42a, and 42b in FIG. 4 for any one position of the second cam member 41 by rotating cam member 41 about the pivot 50.
A control circuit arrangement determining the positioning of the cam members will now be described with reference to FIG. 6 which shows a schematic diagram illustrating the five photoelectric devices 9, 10, 11, 12 and 13 shown in FIG. 1 with their outputs applied to a number of inputs of a control arrangement 61. The control arrangement includes, in effect, a translator which may be based, for example, upon a diode matrix providing outputs upon leads 62, 63, 64 and 65 according to the inputs and a predetermined key. The outputs on the leads 63, 64, 65 and 62 operate solenoid valves 66, 67, 68 and 69, which control the double acting cylinders 22, 30, 31 and 51 respectively. Thus, if the code received by the control means 61 from the photoelectric devices 9 to 13 indicates that the body profile is such that the cam member 15 should be in the position 15a, FIG. 2, and that the cam member 27 should be in the position 27a then a code converter or translator in the control means 61 will provide signals on the leads 63 and 64 resulting in the operation of the cylinders 22 and 30. It is, of course, possible for a spraying programme to begin with one particular cam profile arrangement and for an additional photocell or other detector to be positioned to indicate that there is a change of profile before the programme has finished. In such a situation it is possible, by feeding the further information from the additional photocell to the control means to arrange that the code converter in the control means modifies its output and varies the cam profile accordingly. Alternatively, provision for this change may be programmed into the control arrangement 61 according to a profile originally recognized by the photoelectric devices so that the change occurs after a given time interval from the beginning of spraying. A further control signal may also be provided from the control arrangement 61 to operate a cylinder for positioning the pivot 50 vertically as mentioned above. Instead of cylinders, other well known positioning means, for example rack and pinion and ratchet and pawl mechanisms, may be used.
As has been mentioned above, other means of control of the cam operating cylinders may be provided, for example a code may be set up on the hanger or truck, not shown, carrying the body which can be read, for example, mechanically and the control means may be programmed to operate the cylinders accordingly. Alternatively, the coded information may be read in the control arrangement 61 from a punched tape, which has been coded in sequence, in synchronism with the approach of a respective body to the spraying apparatus. The coded information on the tape may be fed after reading directly to the adjusting means or it may be converted as required.
Referring to FIGS. 7, 8 and 9 there are shown diagrammatic representations of longitudinal sections through a spray gun guiding arrangement at different levels within the side unit 2. In each of the representations the spray gun 4 is shown attached to and freely pivotablc upon an arm 70 which is slidingly arranged within guide bearings 71 and 72. 'Ihe arm 70 is coupled via a U-shaped bracket 73 to a guide block 74 which runs on a rod 75. The whole of the assembly forms a part of a carriage which is reciprocated vertically within the side unit 2. Attached to the carriage there is an air cylinder 77 having a piston indicated at 78 and a piston rod 79 to which there is pinned a stop collar 81 and which carries, freely pivoted at its end, an arm 82 carrying a bracket 83 pivoted at 83a attached to the spray gun 4.
The arm 70 carries a roller 84 at its end opposite to that attached to the gun 4 and the roller 84 moves in the U-shaped channel section of the cam members previously described upon the cam track indicated diagrammatically at 85.
The arrangement is such that during normal spraying the gun 4 is held horizontally. This result is obtained by introducing air into the cylinder 77 on the piston rod side of the piston thereby the stop collar 81 holds the roller 84 against the cam track 85 at a reasonably low pressure so that the gun 4 is held in a horizontal position and the piston is displaced by the same amount as the spray gun 4 and the roller 84. In the two positions illustrated in FIGS. 7 and 8 the effect of this action which results in the gun following both the cam and the profile of the surface being sprayed while remaining horizontal can be clearly seen.
In the illustration shown in FIG. 9 the painting of the body is finished and the gun and carriage assembly have reached the bottom of their travel in the side unit and are at rest. In this position it may be necessary to purge the gun of fluid within it and in order to perform this operation the air pressure in the cylinder 77 is reversed to urge the piston in the opposite direction and the piston rod 79 moves out of the cylinder and causes the spray gun to be tilted forwards so that the purged liquid enters into a spray booth tank, not shown, provided for the purpose.
1. Apparatus for coating surfaces of a succession of articles of different shapes and sizes by a spray gun reciprocable along a path in a first plane during movement of the surfaces past the gun-along a path in a second plane at right angles to said first plane, comprising sensing devices located along the path of the articles and operable to sense the shape and size of the articles, a cam formed by at least two profile-forming members supported for movement relative one to the other to vary the profile of the cam and to control the movements of the gun in said first plane, profile-forming member adjusting means, and control means connected with said sensing devices and said profile-forming member adjusting means and operable to actuate the profile-forming member adjusting means to vary the profile of the cam according to the form of the surface to be sprayed during reciprocation of the spray gun to maintain the position of emission of liquid from the spray gun substantially at a predetermined distance from the surface being sprayed.
2. Apparatus according to claim 1, wherein the profile-forming members each include a U-section channel, and a cam profile-forming strip extending lengthwise of the bases of the U-section channels, said channels being pivoted one to another and movable about their pivots by the adjusting means to vary the profile formed by the strip and to effect curving of the strip between adjacent ends of the channels.
3. Apparatus according to claim 1, wherein there are first and second profile-forming members each consisting of a U-section channel, and a cam profile-forming strip extending lengthwise of the bases of the U-section channels, the channel of the second member being straight along the length thereof and the channel of the first member having a straight portion terminating in a curved portion adjacent one end of the channel of the second member, the adjacent ends of the channels being secured to brackets pivotable about a fixed pivot and the ends of the channels remote from each other being connected to said adjusting means.
4. Apparatus according to claim 1, wherein there are first, second, and third profile-forming members each consisting of a U-section channel, each said channel being straight along the length thereof, a cam profileforming strip extending lengthwise of the bases of the channels, arms secured to opposite ends of the channels of the second member and extending in opposite directions at right angles thereto, a rocking arm rockable about a pivot therefor, said rocking arm carrying pivots at the opposite ends thereof and having said arms pivoted on said pivots, and brackets secured to the ends of the channels of the first and third members adjacent the opposite ends of the channel of the second member, said brackets being pivoted one on each of the pivots carried by the rocking arm and the ends of the channel of the first and third members remote from the channel of the second member being connected to said adjusting means.
5. Apparatus according to claim 4, including further adjusting means for rocking the rocking arm about its pivot.
6. Apparatus according to claim 2, wherein the adjusting means includes fluid-operated cylinders having pistons connected to the pivotable parts of the cam structure. 7
7. Apparatus according to claim 3, wherein the adjusting means includes fluid-operated cylinders having pistons connected to the pivotable parts of the cam structure.
8. Apparatus according to claim 4, wherein the adjusting means includes fluid-operated cylinders having pistons connected to the pivotable parts of the cam structure.
9. Apparatus according to claim 5, wherein the adjusting means includes fluid-operated cylinders having pistons connected to the pivotable parts of the cam structure.
10. Apparatus for coating surfaces of a succession of articles of different shapes and sizes by a spray gun reciprocable along a first path in a first plane during movement of the surfaces past the gun along a path in a second plane at right angles to said first plane, comprising in combination:
sensing means located along the path of the articles for sensing the size and shape of the articles;
a spray gun and means for moving said spray gun along said first path;
variable profile cam means disposed along said first path and engaged by said means for moving the spray gun for controlling in and out movements of the gun relative to said second plane as it is moved along said path in said first plane; and
control means for varying the profile of said cam means in accord with the size and shape of the articlc sensed by said sensing means to maintain said spray gun substantially at a predetermined distance from the surface of an article being sprayed.