US2293815A - Controlling apparatus for presses and the like - Google Patents

Description

M. E. GATES Aug. 25, 1942.

CONTROLLING APPARATUS FOR PRESSES AND THE LIKE 2 Sheets-Sheet 1 Filed Dec. 4, 1939 llllll lu l Aug. 25, 1942.

M. E. GATES 2,293,815 CONTROLLING 'AIPARATUS FOR PRESSES 'AND THE LIKE Filed Dec. 4, 1939 2 Sheets-Sheet: 2

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Major E. Gates, Crystal Lake, Ill. Application December 4, 1939, Serial No. 307,427

- accoml lwing drawings! In said drawings: Fig. 1 is a sectional elevation of a mechanical press equipped with apparatus for automatically regulating pressures;

Fig. 2 is an elevation partly diagrammatic in character of the regulating apparatus;

Fig. 3 is a section thereof taken on the plane 3-3 of Fig. 2; and

Fig. 4 is an elevation similar to Fig. 2, illustrat ing a diiferent form of regulating apparatus.

In presses and many other types of apparatus, no means have been provided for reliably determining the magnitude of the force applied, i. e., whether it is less or greater than the proper force, nor for efl'ectively controlling the force applied to secure uniform treatment of successive articles. For example, in a mechanicalpress it has heretofore been impossible to apply a predetermined compression to an article or to ascertain whether the compression actually applied was too great or too little. In a brick press, to refer to a specific case, variation in moisture content, grain size. wear in machine parts, etc.. results in variation of the force applied by the .press. The brick may be underpressed or overpressed and no means are provided for ascertaining the extent of departure, if any, from the correct pressure, despitethe fact that overpressing or underprwsing produces an inferior brick. This is of particular importance in fire-brick whereunderpressing or overpressing shortens the life of the brick. The same applies to many other pressed articles.

In a mill for rolling sheet metal, to refer to another example, it is important that the sheet delivered be uniform in thickness throughout. For many uses, such as deep drawing, even slight variations in sheet thickness are objectionable. Yet such variations do occur because of variations in temperature and malleability of the sheet and its thichies as it 'enters the rolls. These produce varying strains in the roll stands which alter the spacing of the rolls. Control of the roll spacing in response to pressures exerted 7 Claims. (CI. 18-16) shit thickness withfewer passes through the re The invention is here illustrated as applied to a brick press. The press in this instance is a so-called Boyd press, details of which are dis-.

closed in Patents Nos. 985.153 and 987,124. It will be understood, of come, that the invention is not limited to a brick press and that the details of such press form no part of the invention. Only so much of the press as required to disclose the invention is illustrated in the drawings. For

.complete details of this specific type' of press,

reference is made to the aforesaid patents.

In general, the press comprises a stationary brick mold ID, the upper and lower faces II and I2 of which are movable relatively to each other and to the mold III. The upper face Ii is embodied in a plunger is slidable vertically on the side bars H and operated in this instance by toggle links is and it. The bearings ii for the upper toggle links are carried by the side bars I! adjacent their upper ends. The lower face I: of the mold also comprises a plunger is vertically slidable on the side bars II and supported in its lower position on the crosshead l9 extending between and connected to the lower ends of side bars is. The plunger i3 and the toggle links are, in this instance, operated by a connecting rod 2t 'reciprocated by the crank 2! of crank shaft 22 and connected to the toggle links at the intermediate bearing 23. The drive for the crank shaft 22 is here shown as a drive pinion 2t and gear wheel 25 connected with the crank shaft. Reciprocation of the connecting rod thus efiects a reciprocation of plunger Ii. Maximum compression is delivered to the brick 26 in the mold when the toggle arms is and I6 are practically in alignment as in Fig. 1 where they are shown approaching alignment. In; that position the lower plunger is is supported on crosshead I9 and the side bars I6 assume thestresses developed during the compression of the brick. As shown in Fig. 3, these bars are of substantial section, being in. the case of a multiple brick mold about 5"x7" in section.

To efl'ect discharge of the brick and subsequent filling of the mold with clay, the entire assembly of side bars, plungers, etc., is. made slidable in guideways 21. Vertical movement of the assembly is eflected by the cam action of connecting rods 20 'on cam roll 28. The cam on the sheet will produce greater uniformity in surface 29 on the connecting rod is so designed that when the latter is retracted (to open the toggle) the entire assembly is elevated to bring the lower face I! of the plunger flush with the are in alignment or dead center.

face of the stationary mold to permit discharge of the compressed brick. At the same time the opening of the toggle considerably elevates upper plunger I3. Thereafter the lower plunger recedes a predetermined distance and the slidable hopper 3| passes over the mold cavity and fills the same level with a fresh charge, After the hopper is withdrawn the upper plunger again descends to compress the clay in the mold.

Adjustment of the amount pf clay placed in the mold is effected by varying the elevation oi the face l2 of the mold at the time the charge is deposited therein. As here shown, the plunger I8 is resiliently urged upwardly by spring 32 after the compressed brick has been discharged. This upper position is regulated by an adjustable lever 33 whose end 34 engages the stop element 35 carried by the plunger l5, thereby limiting the level of the face- II at the time of filling the mold. A regulating screw 35 controls the position of lever 33. Upon compression of the brick, the plunger is again forced down upon the crosshead I9.

I have discovered that the magnitude of the pressure delivered to the brick may be determined by measuring the elongation of the side bars H at the instant of the delivery of maximum pressure. Despite the substantial section of these side bars, they elongate appreciably -under the stress exerted thereon. In the present type of multiple brick press, the maximum stress is in the neighborhood of 500 tons and the elongation of the side bars is several thousandths of an inch. In the present apparatus, I utilize such elongation to regulate automatically the maximum pressures delivered by the press. This regulation is effected in this instance by adjusting the volume of the mold by means of the regulating screw 35.

The illustrative extensometer employed in this instance comprises a bar connected at its end 4| to the side bar and extending along the side bar to a control switch 42 operated by the relative movement between the side bar and c extensometer bar 40 when the former is elongated under stress. The control switch in the apparatus illustrated in Fig. 2 comprises a pair of contact points 43 and 44 adapted to be engaged by the projection 45 on the extensometer bar. The contact points are mounted on a vertically-adjustable plate 45 slidable in guideways 41 carried by the side bar l4. Mounting plate 45 is urged in one direction by springs 48 and is held in adjusted position by an adjusting screw 49. The separation between the contact points 43 and 44 is regulated by an adjusting screw 50 by means of which one of the contacts can be adjusted relatively to the other.

The contacts control the mechanism for adjusting the regulating screw 35. In the present thus limiting the circuits is here shown in the form of a switch 54 under the control of crank shaft 22. and closed thereby during the time The device for I Various devices for rendering the circuit operative at predetermined times in the cycle may be employed. That here shown comprises a cam member 55 carried by a shaft and engaging the switch lever 55 to close the circuit only during the time the lever is under the control of the cam member. The cam member 55 is advantageously made removable to permit variation in the point of closing as well as the length of the period during which switch 54 is closed. Generally for a press of this kind the switch 54 is closed only for a very short time, the adjustment required being very small.

When properly adjusted the projection 45 on the extenso meter bar (at the instant of maximum compression) engages contact 44 if the compression is excessive and engages contact 43 if it be deficient. Neither contact is engaged when the compressive force is neither excessive nor deficient. ,When energized, motor 5| adjusts the regulating screw in one direction or another, depending upon whether the compression is excessive or deficient. If excessive, the regulating screw is adjusted to reduce the volume of the mold and when deficient to increase the volume of the mold. The adjustment, if any,

versible motor 5| is of the series typ being relatively slow in starting. Since the interval during which the circuit is operative is relatively short, the extent of adjustment effected by the motor at any given cycle is thus relatively small.

The contacts 43 and 44 may advantageously be in the form of micro switches.

name. The details thereof are disclosed in Patent No. 1,960,020. These switches require a movement of as little as .0002 (two ten-thousandths) of an inch to shift the contact points 'from open to closed position and vice versa.

However, ordinary contact points properly insulated from each other may be employed instead. In that event the projection 45 serves as a contact point and it should be properly connected in the circuit. Condensers should preferably be employed across contact points if sparking is excessive.

In the circuit illustrated, one side of each of the contact switches is connected to the line wire 51. The other side 58 of the line is connected through the control switch 54 to the common terminal 59 of the reversible motor 5|. The other two terminals 50 and 5| are connected respec- ..tively to the remaining terminals of contact switches 43 and 44.

A somewhat simplified control system is illustrated in Fig. 4. This system eliminates the neutral position and a circuit is closed on each cycle. Only one contact member 52 is employed.

the press is exerting its maximum. compression.

Such contact member may advantageously be a micro switch. The switch is carried on an adjustable plate 53 similar to the plate 45 and vertical adjustment thereof relative to the extensometer projection 45 is preferably effected in the same manner, As here shown, the switch is normally closed (i. e. normally engaged by the .extensometer bar).

The switch controls a relay 64 having a double throw switch 55 which is normally closed (when the relay is unexcited) on contact 65. When Such switches may be obtained on the open market under that i energized, switch it makes contact with the other switch point 61. The common terminal a of reversible motor is connected to the line through the phase control switch it operated in v the same manner as in the circuit illustrated in Fig. 2. The relay contacts 66 and 51 are respectively connected with the forward and reverse terminals 69 and of motor 5|. When switch 62 is open, a circuit is established through relaycontact $1 and the motor is rotated in a directlon to reduce the volume of the mold. On the other hand, if the pressure delivered by press be deficient, switch 62 .will remain closed and eil'ect a rotation of the motor in reverse direction, 1. e. to increase the volume of the mold. Preferably contact 62 is adjusted relatively to the projection 45 so that when the compression is the greater the adjustment. If the compression be deficient, the switch remains closed for sub stantially longer period than it is open, if it be opened at all.

With an appropriate rearrangement of the control circuits, the switch 62 may be placed on the opposite side of the extensometer projection 45, i. e. in the same relative location as switch 44,

In that event the switch will normally be open and will be closed when the compression is excessive.

It will be understood that the extensometer may be connected with other portions of the press under strain responsive to the force exerted by the press. The part to which the extensom eter is attached may be strained'either in tension or compression; In presses the element or elements under tension are generally more conveniently and easilyequipped with the extenscmeter. The regulation or adjustment controlled by the extensometer depends, of course, on the article operated on by the press. In the present type of brick press regulation is advantageously effected by varying the volume of the mold. In other presses, adjustment may be effected, for example, by adjusting the approach of the dies, as by elongating or shortening a die plunger or its connecting rod, or by elevating or depressing a stationary die.

In wide presses, such as a multiple brick press, extensometers may be applied to each of the side bars I4 and each may independently control'ad-' justing for its side of the press. In brick presses, for example, it often happens that the condition of the clay in the molds on one side of the press will be different (as regards porosity, etc.) from that at the other side, and thereby require a diiferent adjustment.

Control by power consumption is not a satisfactory method of producing uniformity of product. Powerconsumed is not necessarily proportional to pressures exerted. In a press, for example, the maximum power consumption does not generally occur at the instant of greatest pressure, since at that point there is very little movement.

In the control of rolling mills, an,- extensometer applied to the roll stands may be employed to adjust the roll spacing to secure greater uniformity in sheet thickness. Thicker, cooler, or less malleable sheets would prcduce relatively higher stretch in the roll stands, resulting in a relatively reaterroll spacing and a thicker sheet.

;The extensometer in response to such higher stretch would. compensate therefor by reducing the roll spacing. .The opposite would occur for a thinner, hotter or more malleable sheet. A

rolling mill thus controlledwould produce sheets I of greater uniformity in thickness with fewer passes through the rolls.

Obviouslythe invention is not limited to the details of the-illustrative apparatus since these may be variously modified. Moreover,-it is not indispensable that all features of the invention be'used conjointly since various features may be used to advantage in different combinations and sub-combinations.

'Having described my invention, I claim:'

1. In apparatus for exerting pressure on mate rlal, the combination comprising pressure applying means, supporting apparatus therefor including a structure for assuming the reaction of the pressure applying means, devices forregulating the pressureiexerted by said pressure applying means, an extensometer associated with said structure and responsive to the stresses therein set upby the pressure then being applied by said .pressure applying means, mechanism .controlled by said extensometer for operating said devices to regulate the pressure subsequently to be applied, and means for rendering said extensometer inoperative except the maximmn pressure is exerted.

, 2. In a press'or the'like, the combination com-= prising a :press mold having an adjustable bottom, means for cyclically applying pressure to material in the mold, a structural element in the press assuming abortion of the reaction created 'by the pressure applying means and subject to a strain proportional to the pressure applied, an

extensometer associated with said element and responsive to the maximum strain therein, andthe pressure applied, an extensometer associated with said element and responsive to the maximum strain therein during a given cycle, and means controlled by 'said extensometer for varying the volume of the mold for the next cycle.

4. In a press or the like, the combination comprising a pressmold, means for cyclically applying pressure to material in the mold, a structural element in the press assuming a portion of the reaction created by the pressure applying means and subject to a strain proportional to the pressure applied, an extensometer associated with said element and responsive to the maximum strain therein, and-means controlled by said extensometer for varying the volume of the mold inversely in accordance with variations in the maximum pressure applied on the preceding cycle to adjust the maximum pressure to be applied during the next cycle.

'5. In an apparatus of the character described, the combination comprising means for mechanically applying force to an article, a structural during the period when element in the apparatus assuming a portion of the reaction created by the force applying means and subject to a strain proportional to the pres sure applied, an extensometer associated with said element responsive to strains in said element under the force then being applied, and mechanism controlled by said extensometer for varying the force to be subsequently applied.

6. In apparatus of the character described, the combination comprising means for mechanically applying force to an article, a structural elemenlt in the apparatus assuming a portion of the reaction created by the force applying means and subject to a strain proportional to the force applied, an extensometer associated with said element and having electric switches closed in response to strains in said element caused by the forces then being applied, and means including a reversible motor controlled by said switches for adjusting said force applying means to vary responsively to said extensometer the force subsequently applied by said force applying means.

7. In apparatus of the character described, the combination comprising means for mechanically applying tome to material, a structuralelement in the apparatus assuming a portion of the stress in the apparatus created by the application or the said force and subject to strain proportional to the force applied, an extensometer associated with said element responsive to strains in said element caused by forces then being applied, means including a reversible electric motor for eflecting a variation of the force applied, and circuits controlled by said extensometer for operating said motor to vary the force subsequently applied inversely with the said strain in said element. l

MAJOR E. GATES.

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