US3262420A

US3262420A - Coating and oven system including work handling means

Info

Publication number: US3262420A
Application number: US267020A
Authority: US
Inventors: Bossi Giovanni; Pasqualini Bruno
Original assignee: GALVARPLAST SNC
Current assignee: GALVARPLAST SNC
Priority date: 1962-03-22
Filing date: 1963-03-21
Publication date: 1966-07-26
Anticipated expiration: 1983-07-26
Also published as: GB955792A; DE1234594B

Description

July 26, 1966 G. BOSS] ETAL 3,262,420

COATING AND OVEN SYSTEM INCLUDING WORK HANDLING MEANS Filed March 21, 1963 5 Sheets-Sheet 1 lnventorg Giovanni, 508 Bruno Pasquahnb,

A former/s July 26, 1966 G. 50551 ETAL 3,262,420

COATING AND OVEN SYSTEM INCLUDING WORK HANDLING MEANS X 'i' 47 48g V W" P W 46 fig 46 I I: H w' INVENTORS Giovanni 3035i & Brwzwfaagualini ATTORNEYS July 26, 1966 G. BOSSI ETAL COATING AND OVEN SYSTEM INCLUDING WORK HANDLING MEANS Filed March 21, 1963 5 Sheets-Sheet 5 5 s m m@w m a%o W a ww sa WA 7 35 La W? W o 3% 0w 5 \IOQM.

United States Patent 3,262,420 CQATING AND OVEN SYSTEM INQLUDING WORK HANDLING MEANS Giovanni Bossi and Bruno Pasqualiui, Varese, Italy, assignors to Gaivarplast S.N.C., Varese, Italy Filed Mar. 21, 1963, Ser. No. 267,020 Claims priority, application Italy Mar. 22, 1962, 5,538/62, Patent A/21,673 6 Ciaims. (Cl. 118-57) The coating of articles with plastics or other materials by dipping them into baths of suspended or, as it can also be said, fluidized powder or better into fluidized beds has been applied more and more in the last years. The process consists of placing an article into a heated oven for a certain time depending on the size of the article and the desired thickness of the coating after the surface has been preferably treated with a so-called wash primer, dipping the hot article into a fluidized bed for some seconds, drawingit out and putting it into the ovens again for a fraction of a minute-for the time required for the so-called fusion or postheatingand removing it after it has left the post heat oven and has cooled almost completely. As the characteristics of the coating operation depend on various factors, such as the temperature and the heat accumulation within the article during the time or times of the stay in the oven or ovens as well as the dipping time, it becomes evident that a treating process with continuously uniform conditions should be observed if a mass produced article is to be coated. Because of this necessity and according to the cycle of the process, the designers of installations suitable for the process constructed semiautomatic or automatic systems, with complete closed circuit conveyor chains which move the article to be coated through one or two tunnel ovens.

The installations or apparatus of this type are, in general, big and expensive since they contain one or two tunnel ovens of considerable length. This fact, as well as other disadvantages mentioned hereafter, make these installations suitable only for coating mass produced articles and not for single pieces or pieces produced in small quantities. The huge dimensions of such installations are already a disadvantage in itself, namely because of the high operating and maintenance expenses, the space required, etc. Although the process is cyclic, the duration of the individual phases differ greatly from one another and the designing of the installation has to take care of these periods of different duration. Due to this, difiiculties in the automation of the individual operations arise as well as losses of energy in form of losses of heat either by the ovens or by the articles on their way, as well as losses due to non-working times which cannot be avoided if the continuous cycle is kept up.

It is the aim of the present invention to remove the above-mentioned disadvantages and, in addition, to achieve numerous advantages. The inventor was well aware that the value of the installation is based not so much on the fact that it works semi-automatically, but rather on the fact that it is more productive and better suitable to take care of the individual phases of the process, especially if smaller quantities of different articles are to be coated.

According to the present invention a bell-shaped oven is used, i.e. the opening equipped with suitable doors, preferably with sliding doors, is placed at the bottom of the oven. The bell-shaped oven is placed above a container which contains the fluidized bed of pulverulent material. The oven and the container are connected with each other by a vertically movable car carrying device, called carrier hereafter, moved up and down between the container and the upper part of the oven and which can be stopped in the middle of the way in order to pick up or to deliver the proper car which bears the articles to be coated and which is placed in horizontal rails at the rolling device.

The reciprocating vertical movement of the carrier is mechanical. This movement is achieved by a cylinder with a piston controlled hydraulically which actuates a system of pulleys or sprockets. So, by means of a short piston stroke a long and quick stroke of a rope or chain is achieved which holds the car carrying device.

The same hydraulic device which moves the piston for the carrier serves also for moving two other pistons. These pistons are connected with the half-doors forming the closure of the opening at the bottom of the oven.

Besides, the installation is equipped with a device driven preferably by an electric motor in order to put into oscillation a shaft with a pulley which bears the rope or chain of the carrier with the articles to be coated. The oscillation takes place while the latter are dipped into and immediately after they have been taken out of the fluidized bed. The to and fro motion during dipping is useful in order to make the powder adhere evenly to the surface to be coated, whereas after emerging it serves to remove from the article the surplus powder particles which do not sinter on or melt together. It is of advantage if the installation is equipped with four cars on which the articles to be coated are suspended. While one car is in the oven for some minutes, a workman can take away the finished articles from one of two cars upon which the articles are cooling down and place on a fourth car the articles to be coated. In addition, rolling devices are provided for the installation, which carry rails of the same kind as those of the carrier. These rails are placed at an elevation equal to that where the rails of the carrier stop half way between the oven and the container- The function of the rolling device is to sup port the cars immediately before and after the heating and coating and to receive them from and deliver them to the carrier which runs up and down between the oven and the fluidized bed of powder.

Preferably, the control system of the installation should be operated by means of three levers, the first one serving for opening and shutting the doors, the second one for moving the carrier and the third one for shaking the carrier and the articles respectively. One workman is able not only to operate the control system of the installation but also to take ofl the coated and cooled articles from the car at the end of the line and to make the uncoated parts ready to be moved into the oven. All this is done during'the preheating itme. The workman himself pushes the car with the uncoated parts thus moving the car with the coated parts out of the carrier. This car rolls onto the rolling device arranged on the other side of the oven.

The advantages of this installation are obvious. Gne workman is able to handle all operations even if a great number of different articles has to be coated. This is not possible with the tunnel oven installations described above. Furthermore, it is possible to build several independent installations according to the invention for the cost of one semi-automatic or automatic tunnel oven installation of similar capacity. The bell-shaped oven has little heat loss as the warm air remains in the upper part of the oven; with bell-shaped'ovens, the heating achieved can be with higher etficiency and better economy. The distance which the articles have to move from the oven to the fluidized bed and back is very short, so that also during this operation the loss of heat is very small.

Other objects and advantages of the invention will become apparent from a study of the following description and drawing wherein,

FIG. 1 is a front view partially in section of the apparatus of the present invention,

FIG. 2 is a detail of a portion of the apparatus of FIG. 1,

FIG. 3 is a side view of the structure at the top of the oven in a larger scale,

FIG. 4 is a side view of the rolling device in a larger scale, and

FIG. 5 is a schematic designation of the loading and unloading of the rolling devices.

The installation comprises a container 1 with a fluidized bed'2. The container is put into the ground, preferably in such a way that it lies completely under the floor level 3 of the room in which the installation is mounted. The container is of the common type and the fluidized bed 2 consists of powder which is held in suspension by a bloweralso of the common typewhich is not shown on the drawing. Exactly above the container 1 the bellshaped oven 4 is installed which has the opening 5 at the bottom. The opening 5 has two horizontal sliding doors 6 and 7 with hydraulical movement which will be described later.

Inside the oven, approximately in the middle between the two opposite walls there are two vertical rails 8 of which only one is visible. These rails run from the top of the oven to the floor level 3 of the room. Between the rails 8 runs the carrier 9, consisting mainly of a frame 9 and two U-shaped horizontal rails 9". The carrier 9 is suspended on rope or chain 10. This rope or chain leads through the hole 11 in the top of the oven into the interior part of the oven and is fixed at a fixed point 44. The rope or chain .10 winds itself with fii-turn around the pulleys or sprockets 12 and 13 and is controlled by means of the device 14. The device 14 consists of two series of five pulleys or sprockets 14. The latter are mounted on two parallel movable shafts 14 which can be brought towards or away from each other by means of a hydraulic device which is described later on. The rope 16 Winds itself changeably around an upper and a lower pulley or sprocket, thus forming an advantageous system for hoisting or lifting and lowering the carrier 9. By separating the shafts 14 a movement of the rope is obtained which is the greater the more pulleys or sprockets there arein this case times greater than the movement of the piston of the hydraulic device.

The pulley 12 is mounted on the shaft 12' which is borne by two bearings 15. However, this pulley can be moved vertically in the grooves 15' existing therein. The shaft 12 lies on a cam 16 which give the shaft an up and down movement when turned, together with the pulley 12 and the rope or chain 10. The cam 16 is slidably connected with the shaft 12'. A shaft 16 bears the cam 16 and the sprocket 16" which is driven by the chain 17 which again is driven by the sprocket 18 of the motor 19. The motor 19 is connected with the electric power supply 21 by means of the cable 20, between them there is the switch 22 with the corresponding control lever C.

The installation is also equipped with a hydraulic device 23 with the pump 23. This pump drives the pistons 24-24 and 25-25. The pump is connected with the valves and 31 by means of the inlets 26 and 27 and the

outlets

28 and 29. The valves are equipped with the control levers A and B respectively. Two conduction lines go out from the valve 30; one (32) is connected with the external ends of the cylinders 24 and the other one (33) with the internal ends of the cylinders. The pistons 24 and 24' are placed in the cylinders 24".

Two conduction lines go out from the valve 31; one (34-) to the middle of the cylinder 23" and the second one (35) to the ends of the cylinder.

Pistons

25 and 25 are placed in the cylinder 25".

Each installation has some article holding cars 36 e.g. four on each side of the rolling devices. Each car consists of two opposite arranged frames 46. Between the frames 46 a number of rollers 47 is provided on which with coated articles for cooling.

the car is slidably guided in the rails 39' of the rolling device. Connected with the cars is a number of hooks 48 to which the articles 38 can be attached by further hooks 37.

The rolling

devices

39a, 39b, 39c, 39d (four) form also part of the installation. They consist of two rails 39 which are equal to those 9" of the carrier 9. They are supported by four feet 39 equipped with wheels 45 in order to facilitate the movement over the floor level 3. All rolling devices have the rails in the same height. The sliding of the cars (FIG. 5) goes on as following: In the carrier there are two cars at which coated articles are hanging. In the rolling device 39a (Pos. I) there are two cars with articles prepared for coating. In the rolling device 39b (Pos. II) there are no cars. In the rolling devices 39c (Pos. III) and 39d (Pos. IV) there are cars In the free spaces between the rolling

devices

39b and 39c, 39c and 39d as well as 39d and 39a there are further rolling devices provided which have been left out in the drawing for simplifying explanation.

In order to unload the carrier from cars with coated articles and load with cars at which the uncoated articles are hanging the latter are pushed by the workman out of the rolling device 39a into the carrier whereby at the same time the cars hung with coated articles are pushed out of the carrier into the rolling device 39b by the cars hung with uncoated articles. After the new loaded carrier has been moved into the oven, now the empty rolling device 39a is pushed from the workman from Pos. I into Pos. II, whereby at the same time loaded rolling device 3% is pushed by the rolling device 39a into the Pos. III. The rolling device 39c is pushed by rolling device 3% from Pos. III into Pos. IV and the rolling device 39d is pushed by the rolling device 390 from Pos. 1V into Pos. I. In Pos. IV the cars in the rolling devices are unloaded and loaded with new articles to be coated. The procedure can be started anew, after having finished the coatings and the carrier is stopped in the position between the oven and the container for unloading.

The bell-shaped oven can be heated with any known system. However, it has proved to be of advantage to apply the system shown in the drawing; this system is also part of the present invention. A chamber 40 with an upper inlet 41 to the interior of the oven is placed on one side, or several sides of the oven. In the middle of this chamber a heat exchanger 42 is installed e.g. of nonoxidizing steel. The burners 43 of any type heat the exchanger. Thus, an ascending warm air current arises drawing into the interior of the oven.

The installation works as follows: When the car with the articles to be coated is put in the carrier the workman operates the lever A thus putting under pressure the line 34 and, as a consequence, the car rises to the cover of the oven 4. It is supposed that the oven is warm. Then the workman operates the lever B, thus putting under pressure the line 32, so that the doors 6 and 7 close. The installation should remain in this position about three minutes to heat the articles. After the heating time has passed the workman operates at first the lever B and then the lever A but this time in the opposite direction and longer, so that the half-doors are opened and the articles are dipped into the fluidized bed. Then the workman shuts the doors by means of the lever B and operates the lever C. Thus he switches on the current for the motor 19 which turns the cam 16 by means of 18, 17, 16", 16'. The cam 16 shakes the shaft 12, the pulley or sprocket 12 and finally the article 38. This shaking is necessary to make the powder penetrate into the finest grooves, notches and corners. The dipping time is, in general, short and after the few seconds prescribed the workman opens the half-doors 6 and 7 (lever B), makes the carrier 9 rise again (lever A) till under the top of the oven 4 for the fusion or post-heating phase; he shuts the door (lever B) and stops the shaking (lever C). This phase lasts some fractions of a minute, e.g. 30 seconds. Then, the workman opens the door (lever B) and makes the carrier sink into the position shown in the drawing. Now the next cycle begins for coating articles which hang on a new car.

The rolling

devices

39a, 39b, 39c and 39d can be moved along the rails 145 leading at all Positions I-IV (FIG. 5). These rails can form a closed ring so that the cars pushed by the workman would have to come back to the position from which the workman operates the installation. Thus, he would not have to travel the way from Position I to Position IV at each charging and discharging. The rolling devices between the Positions II and IV are necessary for storing the coated articles for some time because otherwise the articles could not cool down and the coating would not become solid.

It has been experienced that the presence of the rolling devices has proved to be of advantage during the coating operations in order to move the cars and the articles. Of course, there are regulators on the floor level 3 which make it possible to guide the roller devices in such a way that their rails are always in the right position to each other.

The levers A, B and C can be synchronized if necessary, and be equipped with common already existing devices in order to avoid a false operation or in order to simplify the operation itself. Besides, the workman has at his disposal a timer in order to control the exact duration of the phases.

It can be seen from the above explanation that the Workman as well as the installation are occupied continuously. Therefore, it would be impossible to obtain a higher yield, even in an installation of larger dimensions. It is also obvious that it would be useless to strive for continuous automatic treatment. On the other hand it can be pointed out, that the installation requires very little space and that the bell-shaped oven has a very high yield as almost no loss is caused.

The invention has been described and shown only for explanation and without restriction. So it is understood that numerous changes of the whole system and of details can be carried out without, however, giving up the principle on which the present invention is based.

What is claimed is:

1. Apparatus for coating articles with coating substances by dipping heated articles into a fluidized bed of the coating substance comprising acontainer for holding the fluidized bed, an oven above said container, means for heating said oven, doors at the bottom of said oven, means for opening and closing said doors, a carrier for the articles to be coated, hoist means for raising and lowering said carrier whereby said carrier is movable to and from a position in said oven and in said container, means for stopping the movement of said carrier in a position between said oven and said container, holding means for horizontally moving the articles, means on said carrier for receiving said holding means and horizontally moving articles, said hoist means for lowering and raising said carrier including pulley means mounted on parallel shafts arranged to be displaced in relation to one another, and shaking means including a rotatable cam operatively associated with said hoist means to impart a shaking movement to said carrier.

2. Apparatus according to claim 1 wherein said holding means includes a plurality of cars, and said means on said carrier for receiving said holding means including horizontal rails which receive said cars for transporting the articles to be coated.

3. Apparatus according to claim 2 wherein rolling devices are provided adjacent both sides of said carrier to receive the cars from and deliver them to said carrier, said rolling devices including horizontally extending rails, and the rails of said rolling devices and of said carrier being disposed for alignment with each other for the exchange of said cars in said carrier.

4. Apparatus according to claim 1 wherein a control system is connected with said parallel shafts for moving said shafts.

5. Apparatus according to claim 1 wherein said hoist means includes a rope secured to said carrier, a shaft disposed above said oven, a pulley mounted on said shaft, aperture means in said oven, said rope extending through said aperture means and around said pulley, slidable mounting means for said pulley including vertical guides, said shaft being slidably mounted in said vertical guides, and said rotatable cam being disposed against said shaft for imparting a shaking movement thereto and thence to said rope and the articles on said carrier.

6. Apparatus according to claim 1 wherein said oven includes a plurality of side walls, at least one of said walls having a chamber exposed to the top of said oven, said heating means including a heat exchanger being provided in said chamber, and said heat exchanger including at least one burner.

References Cited by the Examiner UNITED STATES PATENTS 22,662 1/1859 ManSley 118425 810,394 1/1906 Clelf 68-10 X 1,332,934 3/1920 Tenca 118-425 1,790,501 1/1931 FOX 11864 1,838,015 12/1931 Von Forster et a1. 266-5 2,263,029 11/1941 Buckner 2264 2,265,849 12/1941 Marsh 2264 2,341,766 2/1944 FOX 2264 2,413,987 1/1947 Maxson 2264 2,458,684 1/1949 Lee 2264 2,498,339 2/1950 Miskella. 2,844,489 7/1958 Gemmer 11721 2,854,044 7/ 1958 Cohen 118-57 X 2,855,193 10/1958 Gilbert 26336 3,136,650 6/1964 Auila 11721 MORRIS KAPLAN, Primary Examiner. JOSEPH B. SPENCER, Examiner.

Claims

1. APPARATUS FOR COATING ARTICLES WITH COATING SUBSTANCES BY DIPPING HEATED ARTICLES INTO A FLUIDIZED BED OF THE COATING SUBSTANCE COMPRISING A CONTAINER FOR HOLDING THE FLUIDIZED BED, AN OVEN ABOVE SAID CONTAINER, MEANS FOR HEATING SAID OVEN, DOORS AT THE BOTTOM OF SAID OVEN, MEANS FOR OPENING AND CLOSING SAID DOORS, A CARRIER FOR THE ARTICLES TO BE COATED, HOIST MEANS FOR RAISING AND LOWERING SAID CARRIER WHEREBY SAID CARRIER IS MOVABLE TO AND FROM A POSITION IN SAID OVEN AND IN SAID CONTAINER, MEANS FOR STOPPING THE MOVEMENT OF SAID CARRIER IN A POSITION BETWEEN SAID OVEN AND SAID CONTAINER, HOLDING