US3376883A - Apparatus for controlling acidulated bath - Google Patents

Description

April 9, 1968 A. DOUTY ET A1.

APPARATUS FOR CONTROLLING ACIDULATED BATH Filed sept. 1, 1965 4 Sheets-Sheet l INVENTORS M wh@ ATTORNEYS April 9, 1968 A. DoUTY ET Al. 3,376,883

APPARATUS FOR CONTROLLING ACIDULATED BATH Filed Sept. l, 1965 4 Sheets-Sheet 2 INVENTORS I 95 ATTORNEYS April 9, 196s Filed sept. l,I

A. DOUTY ET AL APPARATUS FOR CONTROLLING ACIDULATED BATH 4 Sheets-Sheet 5 fr L) A T TOR/V5 ys l April 9, 1968 A. DoUTY ET AL 3,376,883

APPARATUS FOR CONTROLL'ING ACIDULATED BATH Filed Sept. l, 1965 4 Sheets-Sheet 4 INVENTORS awa@ A 7 TOR/VE YS United States Patent 3,376,883 APPARATUS FOR CONTROLLING ACHDULATED BATH Alfred Douty, Wyucote, Dwight E. Buczkowski, Oreland, and James W. Harrison, Wyndmoor, Pa., assignors to Amchem Products, Inc., Ambler, Pa., a corporation of Delaware Filed Sept. 1, 1965, Ser. No. 484,254

7 Claims. (Cl. 137-88) ABSTRACT OF THE DISCLOSURE Apparatus is provided for automatically controlling an acidulated rinse bath for treating metal, which includes equipment for introducing concentrated active chemicals to the bath in coaction with equipment for introducing water for the bath, the equipment being controlled by switching means. The switching means are actuated directly or indirectly by closure of one or more of a group of three initiating switches, and the three initiating switches are respectively operated by a recycling proportional timer, a conductance sensitive relay in conjunction with a conductivity cell, and a level sensing device.

This invention relates to the art of coating metal surfaces. More particularly, it relates to the application of an acidulated rinse over metal surfaces which already have been subjected to the action of conventional phosphate coating solutions.

More specifically, the invention relates to the provision of a simple, novel and relatively inexpensive method and apparatus for automatically maintaining such an acidulated rinsing solution in optimum condition.

Before ldescribing the objects and advantages of the present invention, it will be helpful to consider certain prior art practices as employed in the rinsing of chemical conversion coatings on metal surfaces.

In general, it is known that modern-day phosphate coating or phosphatizing is done in a sequence of events i.e., clean, water rinse, phosphate coat, water rinse, and chemical rinse, i.e., acidulated rinse. The present invention, while relating to the final acidulated rinse, does S in a sequence of phosphatizing wherein an intermediate water rinse is used after phosphatizing and before the final chemical rinse.

In order more fully to achieve optimum corrosion resistance and paint adhesion properties of phosphate coated metal surfaces, it is desirable to rinse such phosphated surfaces with dilute, acidulated solutions containing hexavalent chromium ions and/or phosphoric acid. One of the earlier patents teaching the use of acidulated rinsing solution over phosphate coated metal surfaces is U.S. Patent No. 2,403,126, wherein it is taught that the acidulated rinsing solution may contain from l to 16 ozs; of chromic acid (Cros) per 100 gallons of solution, and that such rinsing solution be maintained at a pH of 2.0 to 4.6.

It was subsequently recognized that enhanced corrosion resistance could be obtained if the acidulated rinsing solutions had dissolved therein other ionic components, such as, for example, nitrite ion, which is taught in German Patent No. 896,892.

However, such acidulated rinsing solutions, even though very dilute, 'are sutliciently acidic to dissolve portions of the phosphate coating and thereby to accumulate dissolved ionic constituents in the rinsing solutions. Attempts have been made to reduce or minimize the dissolution of the phosphate coatings by incorporating into the rinsing solutions suficient cationic constituents so as to preclude the presence of free acid through use of am 3,376,883 Patented Apr. 9, 1968 ice monium ions, as taught in U.S. Patent No. 2,634,225, or polyvalent metal ions such as Ca, Cd, Al and/or Zn, as taught in French Patent No. 1,141,925.

Moreover, it has recently been found that solutions of admixtures of chromium compounds, including both hexavalent chromium and reduced forms thereof, provide enhanced corrosion resistance when employed aS rinses over phosphate coated metal surfaces. Such teachings are found in U.S. Patent No. 3,063,877.

During continuous operation of all of these prior art acidulated rinsing solutions, the salt concentration thereof increases through dragged-in salt contaminan-ts from the water rinse and also as a result of evaporation. Frequently, this salt build-up will continue until a point isv reached Where the acidulated rinsing action no longer imparts any improvement in corrosion resistance, but actually results in reduced corrosion resistance so far as salt spray and humidity tests are concerned.

Various attempts have -been made to overcome this problem of increased ionic concentration in acidulated final rinsing baths. For example, frequent discard of used solutions and replacement thereof with fresh baths has been adopted in some installations, but while this pro- Cedure results in completely satisfactory rinsing lof the' coated metal surfaces, it also creates a serious production bottleneck, particularly in' high speed production, such, for example, as strip line operations.

During operation of these acidulated rinses, several changes tend to occur in their composition. These chan-ges and their causes are as follows:

(l) Depletion of the desirable ingredients, such aS chromic acid, phosphoric acid, etc., which will hereinafter be called active ingredients.

The causes of this depletion in order portance and frequency of occurrence are: (a) Drag-out of the solution by adherence to, or by entrapment in undrained hollowsof the work.

(b) Overflow of the solution because of water not containing active ingredients being dragged in orv otherwise introduced into the solution with a consequent increase in the solution volume.

(c) Chemical action of the solution on the coating on metal. This is generally rather unimportant -as a de` pleting influence but may result in some increase in the amount of undesirable constituents in the solution.

(2) Accumulation of undesirable ingredients, especially ionic impurities.

This may be the result of (a) Dragged in stages. This source of contamination of the acidulated rinse is minimized by providing a prior rinse in overflowing water. Nevertheless, hollow objects are rarely perfectly drained and thus bring into the acidulated rinse considerable amounts of water and remove equivalent amounts of the it certain that the dragged in water is contaminated, for example, with the phosphate coating solution itself. Drag-in and drag-out thus cause both contamination and depletion of the'acidulated rinsing solution.

(b) Chemical action of the metal. This again can be by suitable choice of the erties of the solution.

(c) Partial evaporation of the rinsing solution, which in turn leads to a concentration of the impurities in the fresh water used to make up and replenish the' solution itself. Though not usually very important, this effect may become appreciable when the acidulated rinsing solution is heated to facilitate drying of the emerging metal surfaces.

pH or other chemical prop- It has been customary toV deal with the above effects vwhich tend to occur in these solutions by one of several of decreasing imsolution from previous processingl solution. This effect, too makes.

acidulated rinse on the cooledy minimized but not eliminated means. First or all, any change in solution level has been dealt with by means of a water supply valve actuated by a float or by other means sensitive to solution level. Addition of water in this manner (or any other), in either larger or smaller amounts to the acidulated rinse solution tank, results in an ultimate dilution of the solution in both active ingredients and in impurities.

Restoration of depletion of active ingredient was usually accomplished either by occasional manual addition or by continual pumping from a container of concentrated active material, the solution concentration being checked by occasional chemical analysis as by titration and the replenishing additions being accordingly altered.

Accumulation of undesired impurities was usually overcome by periodically discarding all (sometimes only a portion) of the rinsing solution and replacing it with fresh new solution. The determination of the degree of contamination of the solution has posed a problem of considerable diiculty, So many possible contaminants can contribute to impairment of the coated metal surface, especially its corrosion resistance, blister resistance and adhesion properties for applied organic films, that no rapid chemical tests can be expected to measure accurately the quality of the rinsing solution.

. We have observed that, disregarding for the moment suspended solid impurities and floating layers of organic scum, the most serious contaminants are the ions of s olutes contributed by dragged in coating solution and usually to a smaller extent, by the water supply itself. This has led to the observation that such contributions to the ionic strength of the acid rinsing solution affect its electrical conductance. Accordingly, attempts have been made to use the electrical conductance as a parameter capable, through suitable apparatus, of indicating the existence of a maximum allowable, or excessive, degree of contamination. These indications have been used to operate apparatus to cause introduction of fresh water to the bath and thus to overflow a corresponding amount of the solution whenever its conductance exceeded a predetermined level.

As a method of maintaining the solution in good operating condition, however, this method of monitoring was completely inadequate because conductance alone gave no indication of the amount of active ingredients present.

To effect suitable addition of active ingredients, then a means of monitoring at least one of these, say chromic acid, would be necessary. While such means are available, in theform, for instance, of electro-optical devices sensitive to light absorption in selected spectral regions, such apparatus is expensive, and its use is attended with considerable equipment complications, such as solution circulating circuits for optical absorption cells, liquid filters to remove light scattering solids, etc.

In the provision of complete automation of the controlof a phosphating system of multiple stages, the control of the final acidulated rinse, though important, does not warrant the provision of both conductance controllers for water addition and of, say, chromate controllers with all the associated plumbing and auxiliary apparatus which would be necessary to control solution purity and effective concentration of active ingredients.

In accordance with the present invention, it has been found possible to devise simplified means for chemical control of acidulated rinse water which function effectively to:

(a) Maintain the concentration of active chemical within suitable limits. (b) Maintain the ionic impurity level below an allowable maximum. (c) Minimize the occurrence of floating scum and organic impurities.

We have found that the achievement of these goals is facilitated with a maximum of reliability and a minimum of supervision by providing a combination of means responsive to electrical signals, which will automatically:

(a) Add separately but more or less simultaneously concentrated active rinsing chemicals, and fresh water in constant but adjustable timed increments and ratios, independently of any signal indicating -a departure of the quality of the rinsing solution itself from the standard.

(b) Add both concentrated active chemical and fresh water in a constant but adjustable ratio (preferably not greatly differing from the ratio of active chemical desired in the rinsing bath itself) as required to restore any lost bath volume in response to a signal received from a level-sensing device.

(c) Add both chemical and fresh water in a constant but adjustable ratio in response to a signal generated by an increase of electrical conductive of the solution above a determined level.

In this connection, we have found that the regular periodic addition of chemicals and water to the solution serves in great part to accommodate the depletion of desirable ingredients and accumulations of undesirable ingredients caused by relatively constant processing operations. We have also discovered that automatic additions of water and chemicals in response to conductance and level measurements on the bath in combination with the periodic additions, adequately compensates for those quality changes in the bath which build up only gradually or which are caused by radical fiuctuations in operating conditions caused by production bottlenecks, break downs, unsually high throughput rates and like circumstances.

It is an object of the present invention to provide a method and apparatus for controlling the composition of an acidulated rinse bath of the type employed in the treatment of metal surfaces, which method and apparatus effect the controlled addition of active chemicals and water to the bath during use.

Another object of the present invention is the provision of a simplified method and apparatus for control 0f acidulated rinse baths which obviates the necessity for complex and expensive automatic analytic equipment for control purposes.

A further object of this invention is the provision of acidulated bath control methods and apparatus which are quite exible and adaptable to the needs of a given metal treating operation and readily adaptable to processing variations which tend to occur at a given metal treating operation.

The above objects and purposes together with others may be more readily understood by a consideration of the detailed description which follows together with the accompanying drawings in which:

FIGURE l is a block diagram illustrating the lprincipal components of the invention and the flow of signals and materials between the components, as applied to an acidulated rinse bath;

FIGURE 2 is a simplified diagrammatic illustration of a control system constructed in accordance with the invention;

FIGURE 3 is a simplified diagrammatic illustration of a control system constructed in accordance with the invention which offers certain advantages when compared with the system shown in FIGURE l; and

FIGURE 4 is a simplified diagrammatic illustration of another embodiment of the invention including provision for added flexibility which may be desirable under some circumstances.

Attention is first directed to FIGURE 1 from which an understanding of the basic concepts involved in the invention can be obtained. Three sources of data are utilized. One source is a timer 10, another is a conductance sensor 11, which gathers electrical conductance data from the acidulated rinse bath, and the third is a level sensor 12 which gathers data concerning the level of solution in the rinse bath. l

Each of the data sources or data input means feeds data to a signal generator. Thus, the timer feeds data to the repeating time signal generator 13; the conductance sensor feeds data to the high conductance signal generator 14, and the level sensor feeds data to the low level signal generator 15. The signal generators may be of various types including switches and relays, and it is preferred that they at least generate electrical pulse signals for use by the remaining equipment, though in some cases it may be desirable to use a generator creating a sustained signal.

The signals from the three signal generators are fed to a signal shaping and routing center 16 which in its simplest form -may merelybe a set of wiring for conveying the signals from the generators to the feed actuators. However, in the preferred embodiments the signal shaping and routing center includes equipment for converting signals from the signal generators into sustained signals of pre-determined time length. Preferably the center also includes equipment for creating derivative signals related to the sustained signals in predetermined fashion, which signals are fed to the actuating equipment to operate it.

Concentrated chemicals are fed from a concentrated solution reservoir 17 to the rinsing solution reservoir 18 through the chemical feed actuator 19, which m-ay be an electrically powered pump or an electrically controlled valve. Similarly, water is fed from a source thereof to the rinsing solution reservoir 18 through a water feed actuator 21, which may likewise be an electrically driven pump or an electrically operated valve.

In summary, the invention involves the provision and use of data input means, which measure two key rinse bath parameters, and a time data input means, all of which feed data to signal generators which in turn feed signals to the signal shaping and routing center. Here the signals are shaped and routed and derivative signals are fed to the electrically operated chemical feed actuator and water feed actuator.

. The remaining figures show specifically embodiments of equipment arranged according to the block diagram of FIGURE 1.

In FIGURE 2, three independent switching mechanisms are indicated, respectively, by T-l, CR-l, and by the combination of elements F, R, L, SW-3 in association with the rinsing solution under chemical control which is represented by WS.

In this figure T-1 represents a device which continually and repetitively closes an electric circuit at definite `time intervals and maintains the duration of closure as a selectable proportion of the repetition interval. For simplicity, a device of this kind will be referred to hereinafter as a recycling proportional timer.

The secondswitching device, CR-l, represents a conductivity sensitive relay, connected to a dipping conductivity cell D, and capable of closing an electrical circuit whenever the conductance of the rinsing solution WS exceeds a value which can be pre-selected, as by varying an internal circuit constant such as a resistance by moving a pointer over a dial.A

The third switch mechanism is represented as a float (F) operating to close a switch SW3, via rod R, and bellcrank lever L, whenever the level of liquid WS falls below a predetermined level. The liquid level at which SW-3 is operated may be adjusted by varying the length of rod R, for example. This device does not necessarily include a oat, but may include a pressure sensitive switch operated by changing head of liquid in the tank or other means.

None of the individual switching elements described constitutes a new invention per se. Each of them is commercially available or may be readily assembled from commercially obtainable parts.

The co-action of the above three switching devices is illustrated in FIGURE 2 as follows:

Connection of the lower line of the electric mains P 6 to va common point X occurs whenever any of the switches in T-l, CR-l, or SW-3 is closed. Thus any electrical apparatus directly connected to the upper line of P and to point X is supplied with power from P.

This power may thus, for example, be supplied directly to M-2 and to V-1 by connecting a terminal of each to point X, and the other terminal of each to the upper line of P. Y

M-Z represents a motor driving a pump Q. This pump Q is piped to a reservoir containing a relatively concentrated solution of the active ingredients of the rinsing solution WS. V-1 is an electrically operable valve in a water line connected to the Water mains or suitable reservoir. The pump Q and the water line, through V-l, deliver their contents into suitable regions of the tank containing the solution WS. As mentioned above, an electrically operated valve can be utilized in place o f motor M-2 and pump Q for feeding chemicals, and similarly, a motor and pump can be used in place of electrically .operated valve V-1 for delivering water to the bath.

To function properly, pump M-2 and the water line through V-1 must deliver amounts of active ingredients and of water to WS at rates which are accurately proportioned. Therefore, when operated directly lfrom the power line by one or more of the associated switching means T-l, CR-l, or SW-3, the pump or other means must deliver at an accurately determinable rate. It should indeed be a so-called metering or proportioning pump. The water liow likewise should be accurately determinable and should ibe under the control of a ow regulator.

The recycling proportional timer causes operation of V-1 and M-2 periodically to maintain the concentration of active chemical in the bath. When the level of ionic impurity rises to an objectionable'level, the conductivity sensitive device CR-l operates M-Z and' V-1 to make additions of water and chemicals over and above those added by the proportional timer. Additions initiated by the switching device CR-l usually continue until a certainamount `of overflow of the bath is caused, thereby disposing of a portion of the ionic impurities.

Such overflow also carries olf floating scum and organic impurities. We have found that the overflow resulting from monitoring of the ion impurity level through conductance measurements, is adequate to control not only the ionic impurity level, but also the level of floating scum and organic impurities. The addition of water and active chemicals in response to changes in the liquid level in the bath not only prevents accumulation of undesirable ingredients because of drag-.out and partial evaporation, but prevents the undesirable depletion of desirable ingredients or active chemicals. This is accomplishe-d by adding |both active chemicals and water in response to level changes instead of merely adding water as has been the prior art practice.

A more convenient arrangement, and one which requires of pump Q and the water line through V-1 only relatively constant ow when the pump is running and the valve V-l is open is depicted in the diagram of FIGURE 3. By this scheme only a constant, but not readily readjustable, ratio of the ows is required.

In FIGURE 3, T-2 represents a non-repeating cycle timer. T-2 comprises the driving synchronous motor M-l, the Variable cams D-1, D-2, and D-3, mounted on a cornmon shaft (shown dotted.) The time for each revolution of the common shaft can be selectably adjusted by varying the gear ratio in the drive train between the synchronous motor M-l and the common shaft, for example. Each cam operates the plunger of a switch (D-1S, D-ZS, and D-3S, respectively).

Motor M-1 is conected as shown between the upper line of power line P and common point X of the three switching devices.

When all the switches of T-l, CR-l and SW3 are open, timer T2 is at rest and all of the switches D1S,

D-2S, and D-3S are open. When any one or more of T-1, CR-l or SW-3 close motor M-l is put in operation. As it rotates, it immediately closes all the switches D-1S, D-2S and D-3S`. The closing of D-lS connects the motor M-l across both lines of P and assures the execution of one full rotation of all the cams. When cam D-l has thus rotated to allow the plunger of switches D-1S to drop into the notch, thus opening the switch, rotation of the motor and its shaft will cease, unless at that time one or more of T-l, CR-l and SW-3 are closed, in which case the motor together with the cam assembly will again perform a complete revolution. This rotation will continue until at the time the plunger of DAS drops into its notch, none of T-1, CR-l and SW-3 is closed. The cam system of T-2 then remains quiescent until one of these switches again closes, when the cycle described repeats.

During each cycle of rotation of T-2 it can be seen by reference to FIGURE 3 that switches D-2S and D-3S are closed only for the portion of the cycle time represented by that part of each cams circumference which is high, i.e., which has a great enough radius to operate the plunger to close switches D-ZS and D-3S.

The cams D-Z and D-3 are adjustable so that the relative closed times of switches D-ZS and D-3S are readily variable. It is thus that readily variable precise pumping or water flow-control is made unnecessary. By the arrangement ldepicted in FIGURE 3, it is only necessary to vary the setting of either of the cams of D-2 and D-3 to effect a change in the ratio of the amount of active chemical to amount of Water fed per cycle of T-2.

The advantages of the novel control method will be better understood by a review of some facts concerning a final rising stage as a part of a multistage cleaning and/or conversion coating system for metals.

(l) All of the stages of such a system comprise reservoirs for cleaning, treating or rinsing solution of a size such that rapid variation in the overall chemical make-up in a reservoir is hardly possible.

Therefore, addition of chemical or Water to a reservoir or its associated circulating system need only be made at reasonable intervals-for example intervals of minutes to hours, rather than seconds. Thus, for instance, rinsing chemical and water may be added without stopping for some `fractions of a cycle time of minutes, as dictated by the operation of the cams of non-repeating timer T-2. Only at the end of a cycle of the timer T-2 do the dictates of the switching mechanisms T-l, CR-l and SW-3 effect further additions of chemical and water in the preset ratio.

(2) The concentration of the active ingredients in the acid rinsing solution is not overly critical. Some fiuctuation of this concentration is permissible without appreciably affecting work quality. This has contributed to making possible the present novel, simple, reliable, and relatively inexpensive system of control.

(3) Safety in lthe maintenance of, a low degree of contamination is vitally important even though:

(a) Some accident of processing results in a temporary high rate of introduction of contaminants into the rinse. (b) Evaporation or other cause leads to a decrease in volume of the rinsing solution.

(4) Although the necessary concentration of the act-ive chemical is not overly critical, means need to \be provided to replace the active chemical continually lost by dragout" from the acid rinsing tank. This restoration is accomplished by the action of repetitive timer T-1 which initiates the action of pump motor M-2 and water valve V-l for suitable intervals, say small fractions of an hour, sufficient toefect replacement of solution diluted with nonactive chemical containing solution (by drag-in or by other means). with a suitably diluted mixture of active chemical.

To summarize, it has thus beenfound possible to correctly control within safe limits the composition of au acid rinsing solution of the type described by the following steps:

(l) Providing a device for introducing active chemicals in concentrated form in co-action with a device for introducing water, the ratios of the feed rates of these two devices being controllable.

(2) Both of the above devices operating under the control of switching means which close together or sequentially within a predetermined time interval.

(3) Said switching means being, in turn, actuated directly or through intermediate means by the closure of one or more of a group of three initiating switches.

(4) Said three initiating switches being closed respec- Itively by the action of (a) a recycling proportional timer.

(b) a conductance-sensitive relay in conjunction with a conductivity cell containing the said acid rinsing solution.

(c) a level sensing device operably connected to its initiating switch.

A preferred form of the invention comprises also intermediate means for actuating the switching means which control the said devices for introducing chemicals and water, which intermediate actuating means comprise one or more synchronous non-repetitive proportional timers whose cycling is initiated by the closure of any of the said initiating switches and maintained so long as any of the said initiating switches shall be closed at .the end of the cycle of one of the said timers.

As pointed out above, the concentrated chemical solution and water are preferably added to the bath lby the control system of the invention in proportions adequate to form a replenishing stream having substantially the same concentration of active ingredients as the optimum active ingredient concentration of the bath. This goal is accomplished by adjusting the closure time of the cam operated switches which energize the water valve and chemical pump with respect to each other and with respect -to the constant delivery rates through the valve and pump. This adjustment is readily achieved by varying the profiles of cams D-Z and D3 of the embodiment of FIGURE 3.

We have found in some metal treating installations, so much water is dragged into the acidulated rinse tank and so much working solution is dragged out in normal operations, that Ithe addition as above outlined of concentrated solution and water in ratio to provide a make up stream approximately equal to the optimum bath concentration is not suflicient to keep the strength of the bath at the proper level. Nevertheless, we have also found that simple adjustment of the chemical and water addition ratios to supply stronger make up solution was not a completely satisfactory remedy. The reason for this is that when such extra strong solutions are added in response to a signal indicating undesirably low electrical conductance, the high conducting make up solution causes undesirable distortion in the conductance measurements.

The embodiment of the invention shown in FIGURE 4 shows a form of the invention which is suitable for use under the severe operating lconditions just mentioned. In accordance with this embodiment, the concentration of active chemicals in the make up stream is higher when addition of the material is initiated by the recycling proportional timer than it is when it is initiated by the conductance sen-sing device or the level sensing device. Thus, under the lpreferred mode of operation of this embodiment the make up solution added in response to the recycling proportional timer signals is enough stronger than the optimum concentration of lthe rinse bath to restore the depleted active chemical which is lost because of drag-in of water vand drag-out of solution. We have found that the repetitive timer signal is lthe best initiator for adding extra `strong make up solution Abecause the depletion caused by drag-in and drag-out occurs at a fairly constant rate and the addi-tions in response to the repetitive -timer signals, when integrated over a period of time, are also achieved at a fairly constant rate.

The additions of make up material in response to signals from the conductance sensor and the level sensor in the embodiment in FIGURE 4 are at a concentration approximately equal to the desired bath concentration and thus at a lower concentration than the timer initiated additions. t

In FIGURE 4, the parts which correspond to parts also employed in the embodiments of the earlier gures are given in the same reference characters. Thus, the acidulated rinse bath is indicated at WS. It is equipped with a oat F, having a rod R which cooperates with lever L to operate Switch SW-3. Similarly, the bath is equipped with a conductance measuring cell D connected to a conductivity sensitive relay CR-l. The Valve V-1 is again located in the water feed line and motor M-Z drives pump Q in the chemical feed line.

Timers T-l and T-2 are modified in this embodiment as compared to the embodiment of FIGURE 3. Timer T-l in FIGURE 4 is equipped with a relay RY having three normally open contacts RY-l, RY-Z and RY-3. The relay is energized upon closure of the switch of timer T-1, and upon being energized closes contacts The non-repetitive time-r T-Z in FIGURE 4-is modified in that the cam shaft of motor M-l now carries tive adjustable cams D-1 through D-5 instead of three such cams. There are also lprovided ve cam-operated switches D-1S through D-SS, one for each cam. In FIGURE 4, cam D-1 and its switch D418 again function to provide electrical power to motor M-1 after it has been started by closure of either the switch of timer T-'1, the switch of conductivity sensitive relay CR-l, or level sensitive switch SW-3. Thus, cam D-l and its switch assure that motor M-l will operate through one full revolution of the cam shaft.

Cam D-2 and its switch D-2S cooperate to energize Velectrically operated Valve V-1 during a portion of the rotation of the cam shaft. Cam D3 and its switch D-3S are arrangedto energize motor M-2 which drives the chemical feed pump for a portion of a revolution of the cam shaft.

Cam D-4 and its switch D-4S are also arranged to energize motor M-2 One side of switch D4S is connected to motor M-2 and the other side lis connectable through relay contact RY-S to the low side of the power line P. Cam D isproled so that it will hold D-4S closed for longer portion of a revolution of the cam shaft than f cam D-3 vwill hold switch D-3S closed. Thus, if relay contact RY-3 is closde, D-4S will energize motor M-2 for a longe-r time period during each cycle than will switch D-3S; on the other hand, 'if` relay contact RY3` is open, closure of switch D-4S will not energize motor M-Z.

Cam D.-5 is positioned to hold switch D-SS closed f during most of a revolution of t-he cam shaft. Cam D5 can be proled substantially like cam D-l if it is desired, and for reasons whichwill appear below, it is preferred that .the high portion of cam D-S atleast cover as large an angle as the high portion of cam D-4, and that the low portion of cam D5 coincide, .at least in part, with the low portion of cam D-l.

In operation the embodiment of FIGURE 4 functions as additions of water and chemicals in response to conductivity signals and level signals is concerned. Thus, closure of conductivity relay CR-l or level sensitive switch SW-S will causel timer T-Z to rotate for one full revolution. During the revolution, switches lD-ZS and D3S are held -closed by cams D-2 and D-3 respectively. Motor M-2 and valve V-1 are operated to effect addition of chemicals and water.

The action of the control equipment of FIGURE 4 in response to timer T-1 differs from the embodiment of FIGURE 3. In FIGURE 4, when the switch of timer quite similarly to the embodiment of FIGURE 3 as far T-1 closes, relay RY pulls in, thus closing contacts RY1, RY-2, and RY-3. Power is delivered to motor M-1 through relay contact RY-l, and the timer T-Z thus begins to rotate. It will rotate at least through one full revolution since cam D-1 holds switch D-lS closed throughout a revolution. As timer T-Z rotates, cam D-S closes switch D-SS, and this results in the relay RY remaining energized for so long as cam D-S holds D-SS closed, even if the switch of timer T-l opens.

At this point it should be noted that relay contact RY-3 is held closed so long as relay RY is energized. Relay contact RY-3 supplies power to one side of switch D-4S, the other side of which is connected to motor M-2. Thus, when switch D-4S is closed by cam D-4, power is available for operating motor M-2 so long as relay contact RY-3 is closed. Cams D-4 and D-5 both have profiles such that they close their respective switches for a greater portion of a revolution of timer T-2 than cam D-3 closes its switch. This means that when the timex- T-l initiates a revolution of timer T-Z, power is delivered to motor M-2 for a longer period than when timer T-Z is operated by CR-l or SW3. Thus, concentrated chemical will be added to the bath for a greater portion of each cycle of timer T-2, and since valve V1 is opened for the same amount of time by switch D-2S regardless of how timer T-Z is started, the ratio of chemicals to water for a cycle initiated by timer T-1 is greater than the ratio in a cycle initiated by CR-l or SW-3.

The proles of cams D1 through D-5 may readily be adjusted in known manner so that relative rates o f addition of chemical and water under commands from CR-1 and SW-3 on the one hand and timer T-l on the other hand may be varied to meet the requirements of a particular installation. These adjustments can be accomplished at a central console where timer T-Z may be located, thus eliminating the necessity for making adjustments at the pumps and valves.

We claim:

1. A device for controlling the composition of an acidulated rinse bath of the type employed in the treatment of metal sur-faces, by the controlled addition of active chemicals and water to the bath comprising: an electric motor driven pump for delivering concentrated solution of active chemicals from a supply thereof to said bath, an electrically controlled valve for delivering Water from a source thereof-to said bath switch means for electrically energizing said pump and said valve upon closure of said switch means, a cycle timer having switch operating elements for said switch means, and having timing means responsive to switch actuation thereof to maintain said timer in activated condition throughout a timed cycle of operation, and a plurality of means for initiating activation of said cycle timer comprisingv a timer switch operated at timed intervals by a recycling proportional timer, a conductivity sensitive switch operatedv by an increase of the electrical conductivity of the bath above a predetermined value, and a liquid level sensitive switch operated by a fall of the level of the bath below a predetermined value, each of the switches of the means for initiating activation ofthe cycle timer being connected between a source of electrical energy and with said cycle timer.

2. A device for controlling the composition of an acidulated rinse bath of the type employed in the;treat ment of metal surfaces, by the controlled addition of active chemicals and Water to the bath comprising: electrically operable chemical feed means for delivering concentrated solution of active chemicals` from a supply thereof lto said bath, electrically operable water feed means for de# livering water from a source thereof to said bath, conf trol switch means for electrically energizing said feed means` upon closure of said control switch means, a synchronous cycle timer having timing switch means for maintaining said timer in activated condition for a predetermined time following activation thereof, and having comprising a conductivity sensitive device including a conductance cell, a switching relay actuated by said conductance cell and including circuit means for varying the value of bath conductance as measured by said cell effective to a-ctuate said switching relay, and a float actuated liquid level sensitive switch operable upon fall of the level of the bath below a predetermined value, each of said activating means being connected between a source of electrical energy and said cycle timer, supplemental control switch means for electrically energizing said chemical feed means, a supplemental cam on said cycle timer output shaft for actuating said supplemental control switch means, a recycling proportional timer having a multicontact switching relay actuated by said proportional timer at predetermined intervals, one contact of said multicontact switching relay being connected between a source ofelectrical energy and said cycle timer, another contact of said multicontact switching relay being connected between a source of electrical ener-gy and said supplemental control switch means, and holding means for said multicontact switching relay for holding it in actuated condition for a predetermined time upon actuation thereof,

3. A device in accordance with claim 2 in which said holding means comprises holding switch means connected ybetween said multicontact relay and a third contact of said multicontact relay, said third contact being connected to a source of electrical energy, and a second supplemental cam on said cycle timer output shaft for actuating said holding switch means.

4. A device for controlling the composition of an 'acidulated rinse bath of the type employed in the treatment of metal surfaces, by controlled addition of active chemicals and water to the bath comprising: electrically operable chemical feed means for delivering concentrated solution of active chemicals from a supply thereof to said bath, electrically operable water feed means for delivering water from a source thereof to said bath, control switch means for electrically energizing said feed means upon closure of said control switch means, a synchronous cycle timer having timing switch means for maintaining said timer in activated condition -for a predetermined time following activation hereof, having an output shaft carrying a first cam for actuating said timing switch means, and further having second and third cams on said shaft for actuating said control switch means, and plural activating means for said synchronous cycle timer comprising a recycling proportional timer, a conductivity sensitive 'device including a conductance cell, a switching relay actuated by said conductance cell and including circuit means for varying the value of bath conductance as measured by said cell effective to actuate said switching relay, and a float actuted liquid level sensitive switch operable upon fall of the level of the bath below a predetermined value, each of said activating means being connected between a source of electrical energy and said cycle timer. 5. A device for controlling the composition of an acidulated rinse bath of the type employed in the treatment of metal surfaces, by the controlled addition of active chemicals and water to the bath comprising: electrically operable chemical feed means for delivering concentrated solution of active chemicals from a supply thereof to said bath, electrically operable water feed means for delivering water from a source thereof to said bath, control switch means for electrically energizing said feed means upon closure of said control switch means, a synchronous cycle timer having timing switch means for maintaining said timer in activated condition for a predetermined time following activation thereof, having an output shaft carrying a first cam for actuating said timingswitch means, and further having second and third cams on said shaft for actuating said control switch means, and plural activating means for said synchronous cycle timer comprising a recycling proportional timer, a conductivity sensitive device including a conductance cell, a switching relay actuated by said conductance cell and including circuit means for varying the value of bath conductance as measured by said cell effective to actuate said switching relay, each of said activating means being connected between a source of electrical energy and said cycle timer.

6. A device for controlling the composition of an acidulated rinse bathof the type employed in the treatment of metal surfaces, by the controlled addition of active chemicals and water to the bath comprising: electrically operable chemical feed means for delivering concentrated solution of active chemicals from a supply thereof to said bath, electrically operable water feed means for delivering water from a source thereof to said bath, control switch means for electrically energizing said feed means upon closure of said control switch means, a synchronous cycle timer having timing switch means for maintaining said timer in activated condition for a predetermined time following activation thereof, having an output shaft carrying a first cam 4for actuating said timing switch means, and further having second and third cams on said shaft for actuating said control switch means, and plural activating means for said synchronous cycle timer comprising a recycling proportional timer, and a float actuated liquid level sensitive switch operable upon fall of the level of the bath below a predetermined value, each of said activating means being connected between a source of electrical energy and said cycle timer.

7. A device for controlling the composition of an acidulated rinse bath of the type employed in the treatment of metal surfaces, by the controlled addition of active chemicals and water to the bath comprising: electrically operable chemical feed means for delivering activechemicals from a supply thereof to said bath, electrically operable water feed means for delivering water from a source thereof to said bath, signal generating means for initiating operation of said feed means comprising a repeating time signal generator, a high conductance signal generator, and a low level signal generator, data input means for each of said signal generating means comprising a timer for delivering time data to said time signal generator, an electrical conductance sensor positioned in said bath for delivering conductance data to said high conductance signal generator, and a liquid level sensor positioned in said bath for delivering liquid level data to said lofw level signal generator, and signal shaping and routing means electrically interposed between said signal generating means and said feed means, including means for converting a signal from any of said signal generating means into a sustained signal of predetermined time length, means for connecting said chemical feed means to a source of electrical energy, means for connecting said water feed means to a source of electrical energy, and means for actuating said connecting means for predetermined fractions of the time length of said sustained signal.

References Cited UNITED STATES PATENTS 2,787,281 4/1957 Word 137-5 2,874,714 2/1959 Pellerin 137-5 3,073,330 1/1963 Fattor 137-93 3,095,121 6/1963 Douty 137--93 3,195,551 7/1965 Russell 137-5 3,292,650 12/1966 Bird 137--93 WILLIAM F, ODEA, Primary Examiner.

W. WRIGHT, Assistant Examiner.

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