Electroplating Apparatus For Simultaneously And Uniformly Electroplating Inside Surfaces Of Annular Bodies

Abstract

Herein disclosed is an improved electroplating apparatus for simultaneously and uniformly electroplating the inside surfaces of a plurality of annular bodies. The electroplating apparatus includes an upright anode disposed within registered bores of the annular bodies with its outer contour equi-distantly spaced from the inside surfaces forming inbetween an electrolyte passage, and adjusting means for adjusting at an equal elvel the effective electric currents flowing between the anode and each of the annular bodies, even when the electric conductivity of the flowing electrolyte differs along the axis of the registered bores due to generation of gases in the electrolyte.

Description

BACKGROUND OF THE INVENTION

The present invention relates to the art of electroplating, and more particularly to an improvement in an electroplating apparatus for simultaneously and uniformly electroplating the inside surfaces of a plurality of annular bodies, such as, cylinders of internal combustion engines.

In a conventional electroplating apparatus for simultaneously electroplating the inside surfaces of a plurality of annular bodies, it is an established practice to pile the annular bodies one over another through a sealing seat. An anode is disposed within the bores of the annular bodies and has its outer contour equi-distantly spaced from the inside surfaces of the bodies to form inbetween an electrolyte passage. Each of the bodies is electrically connected with the negative terminal of an energy source through a lead wire. An electrolyte is forced to flow vertically upwardly in the electrolyte passage so as to effect electroplating on the inside surfaces. The electrolyte, then, overflows the upper surface of the piled annular bodies for recovery.

One of the drawbacks concomitant with the conventional apparatus is that since the bodies to be electroplated are maintained at an equal potential the effective currents flowing between anode and each of the bodies are not an equal level. This is because the electric conductivity of the flowing electrolyte is not an equal level along the vertical line of the piled bodies due to generation of gases resulting from the electroplating operation. This fact invites inconsistency in the thickness of the electroplated layer on the inside surfaces of the annular bodies. That is, the layer thickness of the lower body has a larger value than that of the upper body. Since, therefore, the thickness of the electroplated layer should have a minimum value, the lower body has an electroplated layer of unnecessary thickness. This thickened layer must be gound later to have a proper thickness level. This fact is naturally accompanied by an elongated time period required for the electroplating operation, with the resultantly degraded production efficiency, in addition to the bothering grinding operation. Moreover, the increased thickness of the electroplated layer invites spare consumption of the electroplating material such as chromium and accordingly an increased production cost.

As has been described, on the other hand, the electrolyte is guided to overflow the top surface of the piled annular bodies so as to be discharged into an electrolyte reservoir. A hat member, which covers the top surface of the bodies, must be provided with joints for connecting a discharge tube or the like. In addition to this complicated structure, the sealing between the hat member and the discharge tube will become a cause of trouble, because the hat member must be detachably mounted on the particular top surface for installation of the assembled annular body structure. The degraded sealing will permit leakage of the electrolyte and/or the generated gases, and accordingly will produce a problem of firing or pollution.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide an improved electroplating apparatus free from the above disadvantages.

Another object of the invention is to provide an improved electroplating apparatus for simultaneously and uniformly electroplating the inside surfaces of a plurality of annular bodies.

Still another object is to provide an improved electroplating apparatus, in which an upright anode is disposed within registered bores of the annular bodies with its outer contour equi-distantly spaced from the inside surfaces of the annular bodies for forming inbetween an electrolyte passage, and in which adjusting means adjust at an equal level the effective electric currents flowing between the anode and each of the annular bodies, even when the electric conductivity of the flowing electrolyte differs along the axis of the registered bores due to generation of gases in the electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will be apparent from the description made in conjunction with the accompanying drawings, in which:

FIG. 1 is a partially sectional view of an electroplating apparatus according to the present invention, taken in the vertical line; and

FIG. 2 is a partially sectional view taken along the line 2 -- 2 of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 2, an electroplating apparatus according to the present invention is generally designated at numeral 10, which is used to simultaneously and uniformly electroplating a plurality of annular bodies 11 such as cylinders of internal combustion engines. The annular bodies 11, which are formed with inside surfaces 12 to be electroplated, are piled one over another through an electrically insulating seat 13 in a manner to have their bores registered with each other. That is, each of the seats 13 is interposed between any adjacent pair of the annular bodies 11 so as to electrically insulating the bodies 11 from each other and at the same time to keep hermetically sealed joint between the adjacent pair of the bodies 11, thereby forming an upright tubular body (not numbered). This tubular body rests on a base plate 14 and is assembled into a block by means of elongated bolts 15 which are held at the corners of the base plate 14. On the top surface of the tubular body, more specifically, are mounted an annular head disc 16 and a packing 17 both formed with registered bores, through which the bolts 15 upwardly extend. The uppermost ends of the bolts 15 are threaded so that they are nutted up by corresponding hanging members 18 after a hat 19 has been placed on the packing 17 with its brim portion being fastened to the bolts 15. Thus, the hat 19 is hermetically mounted on the upper surface of the tubular body through the head disc 16 and the packing 17, thereby providing a unitary structure assembled with the tubular body and the base plate 14.

In the outer vicinity of the tubular body is a vertically disposed cathodic conductor 22, hereinafter called "cathode" formed with an upper projection 21. It shoulld be noted here that the cathode 22 has a predetermined intrinsic resistance, as will be discussed later. This cathode 22 is electrically connected with each of the annular bodies 11 through a fastening bolt 23. The location of the fastening bolts 23 may be anywhere with respect to the annular bodies 11, but they should be equi-distantly spaced from any adjacent coleagues.

As better shown in FIG. 2, two guide pipes 24 are inserted into corresponding bores formed in both the base plate 14 and the head disc 16. On the upper surface of an apparatus main body 25, are anchored two guide rods 26 which are inserted into the guide pipes 24 when it is intended to install the assembled block in position on the main body 25. This installment is finished by fastening four arms 27 which are mounted on the main body 25, as shown.

Indicated at numeral 28 is an operating handle acting to mount the projection 21 of the cathode 22 on a cathode plate 29 for rendering electrically conductive the connection between the cathode 22 and the cathode plate 29. This operating handle 28 is electrically connected with the negative terminal of an energy source (not shown) so as to apply a negative potential to the annular bodies 11.

Disposed within the registered bores 12 of the tubular body is an upright anode 31 which is mounted on the apparatus main body 25 in a manner to upwardly extend into the chamber of the hat 19 through the bore 16a of the head disc 16. This anode 31 is made of highly conductive material and is electrically connected with a positive terminal of the energy source by way of an anode plate 33. It should also be noted that the anode 31 has its outer contour equi-distantly spaced from the inside surfaces 12 of the tubular body, thereby forming inbetween an electrolyte passage 35 in which an electrolyte is forced to flow. The outer surface of the anode 31 may preferably be coated with some suitable material 34 having a high conductivity and a sufficient resistance to the attacking of the flowing electrolyte. One of the materials suitable for this purpose is lead.

The anode 31 is not solid but has another electrolyte passage 36 formed therein and defined by an electrolyte pipe 37 which has a sufficient resistance to the attacking of the electrolyte. This electrolyte pipe 37 has its upper end extending into the chamber of the hat 19, thus offering to the electrolyte passage 36 a fluid communication with the electrolyte passage 35 in the particular chamber. The lower end of the electrolyte pipe 37 is, on the other hand, communicated with an electrolyte reservoir (not shown) by way of a discharge pipe 38.

In the anode 31, there is also formed a detergent-air passage 39 for supplying therethrough a detergent or air to the chamber of the hat 19 and to the two electrolyte passages 35 and 36. After the electroplating operation has been completed, the detergent thus introduced acts to clean the chamber and the passages 35 and 36, while the introduced air acts partly to dilute gases remaining in the chamber and partly to scavenge the chamber and the passages. The detergent-air passage 39 has an outlet port 43 of nozzle shape extending into the chamber. At the lower extension of the passage 39 is provided a change-over or two-way valve 41 which changes the connection thereof with a detergent supply and with an air supply, respectively, through pipe branches 42a and 42b. In another modification, the detergent-air passage 39 under discussion may be divided into two pipelets (not shown) each for detergent and air introductions. Then, the change-over valve 41 may be dispensed with.

Indicated at numeral 44 is an electrolyte supply pipe through which an electrolyte is supplied to the electrolyte passage 35 by way of an electrolyte inlet port 25a formed in the apparatus main body 25, as shown. The electrolyte supply pipe 44 is as customary provided with a valve (not shown) for allowing and inhibitting the electrolyte supply to the passage 35. The inlet port 25a is bypassed to an electrolyte-detergent discharge pipe 45 which is provided with a change-over or two-way valve 46. By controlling this change-over valve 46, an electrolyte and/or detergent remaining in the passage 35 and the inlet port 25a are selectively discharged through pipe branches 45a and 45b.

With these construction arrangements, since the anode 31 has already been electrically connected with the positive terminal of the energy source, the assembled block with piled annular bodies 11 to be electroplated is fastened to the apparatus main body 25. Then, by manual handling of the operating handle 28, the projection 21 of the cathode 22 is electrically connected with the cathode plate 29. In the meanwhile, the valve mounted in the electrolyte supply pipe 44 is opened, and the two change-over valves 46 and 41 are closed. At this stage, an electrolyte is pumped into the electrolyte passage 35 by way of the supply pipe 44 and the inlet port 25a. As a result, the electrolyte passage 35 is filled with the incoming electrolyte. At this stage, electric conduction starts to take place between the annular bodies 11 and the lead layer 34 applied on the anode 31, so that the inside surfaces 12 of the bodies 11 are electroplated with the accompanying gas formation in the passage 35. The generated gases, which are in the form of tiny bubbles, are conveyed in the passage 35 by the flowing electrolyte. Since, in this instance, the flow of the electrolyte is directed upward, the conductivity of the electrolyte decreases as it goes up, due to the increasing gas content. This requires a higher bath voltage for the higher annular body 11. It should be appreciated that the above difficulty is obviated in the electroplating apparatus 10 of the present invention by increasing the negative potential of the annular body 11 positioned at a higher level. That is, the effective electric currents flowing between the anode 31 and each of the annular bodies 11 are adjusted at an equal level by compensating the electric conductivity of the electrolyte in the passage 35 differs along the axis of the tubular body. As has been touched shortly, the cathode 22 has a predetermined intrinsic resistance of considerable value, and the negative potential to be applied to any of the annular bodies 11 is smaller than that to the overlying body 11 by a value determined the distance between the two adjoining fastening bolts 23. Therefore, if the intrinsic resistance of the cathode 22 is preset at a suitable value, then the resultant negative potential drop between any adjacent annular bodies 11 will compensate the increase in conductivity of the electrolyte wetting each of the inside surfaces 12 thereof due to the decrease in existance of the generated gases. With this condition being satisfied, the thickness of the obtained electroplated layer on the inside surfaces 12 of the annular bodies 11 is equal along the axis of the tubular body.

After the electroplating operation has been completed, the valve in the electrolyte supply pipe 44 is closed, and the change-over valve 46 in the discharge pipe 45 is turned to have communication with the pipe branch 45b. Then, the change-over valve 41 in the pipe 39 is changed to have comunication with the pipe branch 42b so as to introduce pressurized fresh air therethrough. The air thus introduced scavenge the passage 36, the chamber in the hat 19 and the passage 35, in other words, the air discharges an electrolyte remaining in the latter passage 35 in to the electrolyte reservoir (not shown) through the pipes 45 and 45b.

After the electrolyte has been expelled out of the passage 35, the valve 41 is changed to have communication with the detergent reservoir (not shown) through the pipe 42a, and at the same time the valve 46 is changed to have communication with the detergent reservoir through the pipe 45a, as shown in FIG. 1. Then, a detergent is pumped into the pipe 39 and injected into the chamber in the hat 39 through the nozzle 43. The detergent thus injected falls down in the passage 35 while cleaning the electroplated inside surfaces 12 of the annular bodies 11, and finally is returned to the detergent reservoir.

As has been described in the above, since the conductivity of the flowing electrolyte is uniform everywhere in the passage 35 irrespective of the gradual increase of the generated gases, the resultant electroplated layers formed on the annular bodies have the same thickness. The electroplated inside surfaces 12 of the annular bodies 11 need not be ground or finished to have an equal thickness, as contrary to the conventional electroplating apparatus. The time period required for the electroplating operation is considerably shortened. Moreover, spare consumption of an electroplating material is remarkably reduced.

The electroplating apparatus of the present invention should also be appreciated in the point that it has its discharge pipe formed in the anode and its outlet port formed in the apparatus main body, keeping its hat hermetically mounted on the assembled annular body structure to be electroplated. Thus, the present electroplating apparatus is free from any joint or hose provided at the hat for discharging the remaining electrolyte remaining in the passages of the apparatus. As a result, free emission of noxious gases generated in the apparatus is prevented, which might otherwise invite firing. The apparatus itself can be made highly compact, providing for a simplified handling when in operation.

Claims

We claim:

1. An electroplating apparatus for simultaneously and uniformly electroplating the inside surfaces of a plurality of annular bodies placed upon one another so that their central bores are registered comprising: an upright anode about which said annular bodies are to be placed with the inner surfaces equi-distantly spaced from the outer surface of said anode to thereby define therebetween an annular passage; a plurality of seats respectively separating adjacent ones of said annular bodies to electrically insulate the same from each other; means for forcing an electrolyte through said passage; an elongated cathode conductor for applying a negative potential to said annular bodies; said cathode conductor being substantially vertical and constituting a single member having a considerable intrinsic resistance, said cathode conductor having individual means along its length to apply a different negative potential to each of said annular bodies with the negative potential increasing in the direction of flow of the electrolyte, so that the effective electric current flowing between said anode and the respective annular body is substantially equal even though the electric conductivity of the electrolyte differs along said passage due to the generation of gases in the electrolyte.

2. An electroplating apparatus according to claim 1, wherein said individual negative potential applying means includes a plurality of fastening bolts connecting said single member to said annular bodies and equi-distantly spaced from each other for building up a potential drop therebetween determined by the intrinsic resistance of said single member.