US 3192751 A
Description (OCR text may contain errors)
July 6, 1965 P. N. BAKER 3,
I INDICATORS Original Filed Aug. 25, 1960 haves-r02 fi-rsg NORRIS BHKER uses-ass BY hazy-kw,
Anoanej United States Patent This application is a continuation of co-pending US. patent application Serial No. 51,844 filed Aug. 25, 1960, and now abandoned.
This invention relates to indicators, and particularly to indicators for use with forging presses, for indicating the thickness of an article being forged or for indicating the absence of an article within the forging press.
it is frequently required to know the thickness of an ingot or other article, before the squeeze applied by the press tools occurs; at present, the'thickness is measured by the use of calipers, but this involves a waste of time and requires the presence of auxiliary labour during the forging. Furthermore, the information concerning the thickness is not readily available to an operator who controls the forging operation from a distant point.
This requirement is particularly relevant to known forms of forging press control systems wherein reduction of workpiece tmckness during the forging stroke of a press operation cycle is determined as a preselected proportion of the initial workpiece thickness for the cycle in qustion. In such systems a servo control is employed for press tool closure, which control involves comparison of current press tool separation with a preselected proportion representation of a registered representation of initial workpiece thickness.
Examples of such systems are described in U.S. Patents Nos. 3,036,253, and 2,922,053.
Furthermore, where control of a forging operation is effected by an operator located at a distance from the press itself, that operator might be unable to see when the pass is completed and the input has cleared the press tools. In these circumstances, it is desirable that he should be provided with an indication to that effect.
In accordance with one aspect of the present invention an indicator for use with apparatus for shaping an article under pressure, such as a forging press, has a device which is responsive to the application of pressure to the article and control or display means operated by a signal from the device, or the absence of a signal therefrom;
According to another aspect, the indicator comprises indicating means arranged to indicate the position of a movable part of said apparatus and a device arranged to operate when said indicated position corresponds to a dimension of an article to be shaped by the apparatus.
When the invention is applied to the measurement of r the thickness of an ingot or other article between the press tools or a forging press, there are provided means for indicatin the separation of the press tools, a device which responds on pressure being applied by the tools to the article, and means operated by the device for causing the indicating means to indicate the separation of th press tools when the pressure is applied.
When it is desired to give a control or warning indication when there is no article between the press tools, the device which responds to pressure being applied by the tools to the article is made to operate indicating means when no article is engaged by the press tools.
The invention will now be described in greater detail with reference to the accompanying drawing, which is in part a schematic elevation of a forging press, and in part a circuit diagram of one form of the invention.
The forging press shown in the drawing is generally similar to that of FIGURE 4 the afore-mentioned US. Patent No. 3,036,253, andthe same reference numerals are used. However, a detailed knowledge of this prior figure, other than it concerns a forging press control system of the known form referred to hereinbefore, is not necessary to an understanding of the aspect of the present invention recited in the appendant claims. The moving press member 5% is carried on a cross head 51 which also carries a rack 52. co-operating with a pinion in a gear box 53 which is carried on t..e base 54 of the press by means of a bracket 55. The gear box 53 also carries a rotary potentiometer 56. The angular position of t..e pinion and hence of the slider of potentiometer 56 is thus determined by the position of the cross head 51 relative to the base 54, and hence by the distance between moving press member 59 and the fixed press member 50' located on the base 54.
A hydraulic line 67 carries liquid under pressure for causing downward movement of the press. Other hydraulic connections are not shown.
The potentiometer as is supplied with a known voltage through lines l4, 15. Since the slider is driven by movement of the moving press member 50, the potentiometer gives a voltage depending on the separation of the press This separation is of course equal to the dimension of the ingot in the direction of motion of the moving press tool, at the instant at wmch the tools come in contact with the ingot. The voltage from the potentiometer 56, besides being employed in theknown form of forging press control system as current press tool separation indication in the press servo control, say, is also applied through lines 12 and i4 and a normally closed switch S to an indicator 1. Thus, While the switch S is closed, the indicator I continuously indicates the separation of the press tools. The switch is opened by a device which responds when pressure is initially applied by the press tools to the ingot, and the indicator is such that it does not return to zero, but continues to provide a static indication of the thickness of the ingot before the forging operation is effected. Where it is desired merely to measure the thickness of the ingot without subsequent forging, the signal from the device S may be arranged to stop further movement of the forging press. However, for the purposes of the above-mentioned known control systems,
it is required to know the thickness of the ingot before a switch S connected into the hydraulic supply line 67. Alternatively, where a tachometer T, shown carried by and driven by gear box 53, is employed in the servo control of the known control system to indicate by a proportionate signal the rate of displacement of the moving crosshead El switch 5 may be operated in response to a drop in output from that generator. Again, the switch device Thus, the device may consist, as shown in the figure, of a pressure-sensitive.
may include a microphone mounted adjacent to the hydraulic system and arranged to respond when the pitchthe voltmeter bythe switch 8 then leaves the voltage indicator in the position corresponding to the thickness of the ingot before the press operation occurs. In place of this indicator however, there may be employed a fast acting follow up servo mechanism remotely indicating a position. In this case, the position signal derived from the moving press tool is fed to the servo system which drives an indicating arm. Part of the switch device S is then located the sup ly to the servo motor. As bef tife the motor is isolated; when the press tools engage the ingot and therefore thereafter indicates the initial thickness of the ingot. Again, the tool separation may be sensed by a switching device including a moving ore transformer connected through a switch part to the iiidi cator instead of by the potentiometer; the operation is as before.
Where the device which responds on pressure being applied to the ingot automatically operates the control system for the press to stop the press tool when the ingot is initially engaged, the switch part of device S is not arranged in the circuit of indicator 1, but in the press control circuit, and the indicator may take the form of a voltmeter fitted with an auxiliary pointer which is constrained t6 fdllow tl'iiiiain pointer in one direction but maintains its position when the main pointer reverses its direction of movement.
When swage tools are in iisetthe forging is slewed 56 as to come into contact with the flat portions of the tools, or a biased scale is used for reading the display. Iii this case, a preliminary zeroing operation is necessary in which the tools are brought into contact and the zero of the indicator I is corrected.
When it is desired to give an indication when the ingot has been moved out of the forging press, means may be provided to o erate a warning or control circuit when switch S g'ives no signal during the entire movement of the moving press member. For this purpose an alarm relay ALoperating an alarm circuit (not shown) may be included in the circuit 121 14 of indicator 1. The potentiorn eter is arranged to give an incfeasing voltage with decreasing separation of the press tools, and relay AL is adjusted to act on a voltage corresponding to contact be tween the press tools, or to a predetermined minimum separation of the press tools. Thus relay AL will only operate if the press completes a stroke without operation of switch S.
While the apparatus has been described as having a rotary potentiometer 56 as giving'an indication'of the separation of the press tools 50, 50, a signal according to 1.An indicator for use with cyclically operable 'apjparatus for shaping an article under pressure between press tools comprising indicating means providing an electrical signal representation of the distance of a rejciprocable press member from a predetermined datum position'of such member, and a device causing the indicating means to provide a static representation of the distance of said press member from the predetermined datum 4 position thereof when the article is first engaged by both; the press tools during a cycle of said apparatus.
2. A forging press having a pair of press tools and at least one reciprocable press member for causing closure and separation of said tools, and which press comprises indicating means responsive to said moveable press memher to provide an electrical signal representing the separation of said tools, and a device responsive to engagemerit of an article by both said tools to cause said indieating means to provide a static representation of the current press tool separation.
3. A device for indicating the distance between relatively moveable pressure members, at least one of which is reciprocable, of a hydraulic press when pressure is applied to an article to be shaped in the press, the pressure to effect a pressure stroke being applied to the press through apressure fluid conduit, said device comprising: a position transducer providing a position representative electrical signal, transmission means coupling the re ciprocable press member to said transducer whereby the transducer provides an electrical signal output representing the relative separation of said pressure members, switch means connected in an energising circuit including a'source of current and operable in response to application of pressure by said press members to an article to be shaped thereby to de-energise said encrgising circuit, and maximum-indicating means responsive to the output signal from said transducer and connected in said energising circuit, whereby operation of said switch means to de-energise said circuit causes the indicating means to provide a static indication of the relative separation of said press members when substantially first engaging saidv article.
4. An indicator? according to claim 1 comprising alarm means operable in response to said electrical signal representation when representing a predetermined minimum distance of said press member from its'datum position.
5. A device for indicating the distance between a moveable pressure member and a stationary pressure member of a hydraulic press when pressure is applied by 'the moveable pressure member of the press to an article to be shaped in the press, the pressure to effect a pressure str'olre being applied to the press through a pressure fluid conduit, said device comprising a potentiometer, 'a' measuring instrument and pressure-sensitive switch means connected in an energising circuit including a source of current, transmission means coupling the moveable member of the press to the slider of the potentiometer to displace said slider in accordance with the movement of said moveable member, whereby the indications of said measuring instrument are continuously indicative of the position of the moveable pressure member in reference to the stationary pressure member of the press, said switch means being responsive to the pressure in said pressure fluid conduit and arranged to be operated n response to a pressure above a predetermined value in said conduit, operation of said switch means de-energising said energising circuit, the fluid pressure in said conduit being 'below said predetermined value when and while said moveable pressure member during the pressure stroke of the press is spaced apart from the article to 'be shaped and rising above said predetermined value when the moveable pressure member becomes engaged with said article.
6. A device according to claim 5, wherein said measuring instrument is a maximum-indicating instrument which remains in its position of indication when S Elld switch means are operated to de-energise said energismg circuit, whereby said indication of the instrument is indicative of the distance between the moveable pressure member and the stationary pressure member at the moment pressure was applied to the article.
7. A device according to claim 5 and further comprising signalling means included in said energising circuit,
said signalling means being actuated by a voltage condition in said circuit corresponding to a slider position in- 5 6 dicativ'e of a predetermined minimum distance between 2,922,053 1/60 Steel 307-149 the pressure members. I 2,962,960 12/60 Slater 7842 3,036,253 5/62 Bramley 318-29 References Cnted by the Examiner FOREIGN PATENTS UNITED STATES PATENTS 5 1,128,366 1/57 France 2,018,217 10/35 McNamee 7813 2,827,765 3/58 Towler 7 842 WILLIAM J. STEPHENSON, Primary Examiner.