US2577882A - Forging press - Google Patents

Description

D 11, 1951 J. FOSTER 2,577,382

FORGING PRESS Filed NOV. 23. 1949 dill Patented Dec. 11, 1951 FORGING PRESS John Foster, Openshaw, Manchester, England, assignor to B. & S. Massey Limited, Openshaw, Manchester, England, a British company Application November 23, 1949, Serial No. 128,959 In Great Britain November 29, 1948 3 Claims. (Cl. 1925-144) This invention relates to control gear for presses and forging machines of the kind having a ram actuated by an eccentric shaft, a brake for arresting the eccentric shaft and a clutch for coupling the eccentric shaft to a driving medium. The object of the invention is to provide a convenient electrical arrangement for controlling the press, including means for obtaining a controllable time lag between disengagement of the clutch and application of brake.

According to the invention, switchgear is provided to give continuous running, single strokes, r inching of the ram, and electrical means for delaying the brake application includes an adjustable resistance-capacity timing or delay circuit, with means for adjusting the circuit in accordance with the momentary speed of the motor driving the press.

A convenient arrangement according to the invention is illustrated diagrammatically in the accompanying drawing.

A rotary selector switch has contacts at a for switching on and off, contacts at b for selecting inching or single stroke and continuous opera tion, shown in the position for single stroke and continuous, and contacts at c for selecting single stroke or continuous operation, shown in the single stroke position. A foot lever d is depressed to obtain either single stroke or continuous operation, according to the position of the selector switch, and a push button switch e is used for inching. Current is supplied by the leads I. There is a single stroke cam g actuating contacts h for single stroke working, and a control cam i controlling contacts 7'.

The clutch is controlled by a piston in a cylinder having a solenoid operated spring-loaded air valve, with a small inlet port and a large exhaust port, so that engagement of the clutch' by displacement of the piston on admission of air to the cylinder is slightly delayed, while release occurs quickly. The valve is operated by a solenoid m the current supply to which is controlled directly by contacts 7'. The brake is released by the opening of an air valve mounted on the brake cylinder to give quick release, the valve being opened when a solenoid k is energised and closed by spring means when the solenoid is de-energised. Consequently, when the solenoids k and m are energised the clutch engagement occurs only after the brake has been released. In the circuit of brake solenoid k are contacts actuated by a relay n which can be energised by a low voltage relay n As described below, there is a delay circuit associated with the relay n 1 to give a time lag between the opening of contacts 9' and the opening of the relay contactor, in order to delay the brake application until the clutch has been released.

The drawing shows contacts b and c in the single stroke position. On closing contacts a and depressing foot lever d, a circuit is completed through coil 0 which attracts armature p and thereby closes contacts 9', whereby a circuit is completed through clutch solenoid m and transformer'q, the secondary of which energises relay 1: through a rectifier bridge and thereby causes relay n and consequently brake solenoid k to be energised. Then as stated above the brake is released quickly while the clutch engagement is slightly delayed. The single stroke cam g opens contacts h after a stroke of the press, whereby armature p is released and contacts 7' opened to prevent further operation. A holding coil 1' keeps contacts it open as long as pedal d remains depressed.

For continuous working, contacts 0 are closed, and therefore coil 0 is energised when pedal d is depressed and the clutch and brake solenoids are energised as above and remain energised. When the pedal is released the control cam 1' holds the armature p up until the ram approaches its uppermost positon and then lets it drop to open contacts i.

For inching, contacts 12 are changed over, so that clutch solenoid m and transformer q are energised when push button contacts e are closed.

In parallel with the relay n there are a condenser s and a circuit containing a variable resistance t and a trimming resistance t and two adjustable resistances u, '12 which are normally short-circuited by spring-loaded, electro-magnetically operated contactors w, m, the operating coils of which are connected in series across a rectifier bridge '1 across the secondary of a current transformer 2, the primary of which is in series with one of the phases of the motor supply. When the motor speed drops, its current increases, and the pull on the contactors w, :1: also increases. The spring loadings are such that the contactors open at different values of the current, e. g. one

' half and three quarters of'the maximum ourrent. Consequently when the motor slows down under load, extra resistances are connected in series with resistance t.

The RC circuit in parallel with relay n con- I being connected in series nwith oneanctherland :3

the motor current. Consequently when the motor speed is reduced the application of the brake is further delayed, for the purpose of ensuring that the ram will come to rest as near as possible to its top dead centre position. There may be a considerable reduction of the motor speed duri a h avszm s n 9k An alternatiyef for'rn of delay circuit ,includg a neon lamp, anci' variable and adjustable resistances as described above in series with the relay, coil, with a condenser across the current supply." In this case the relay contactor does notjbpen until the neon arc breaks as thevoltage condenser drops after thecurrent suppl cuit has been opened. The r'eisgii niicsum th directly actuate the contacts he brake sale: noid circuit. w

What I claim is:

1. In a control system for presses and iprging machines of the type haying a ram actuated by eccentricshaft, a brake vfor arrestin the ntric shaft and ,a, clutch" for. coupling, the ntric shaft to' a ar'wm "mediuirizjaclutch operating solenoid, a brake-operating"solenoid, contacts for. connecting the brake solenoidjt'oa current supply source, a 'brake relay Ioraetuating said contacts, switch means for "connecting the clutch solenoid and, the brake relay .to' a current "supply source, a delay circuit associated with the brake relay for retarding th opening 352' ottherelay when disconnected Zfrom lthe current supply source, the delay circuit. comprising a condenserand ayariable resistance and a plurality of a further resistances, said resistances n p l wit the sw mm r: pri ses?! in which the switch means for connecting the clutch solenoid and the brake relay to a current'source comprise push button contacts for inc and electromagnetically controlled conffor single stroke and continuous operation.

- -3 in aicontrol system for presses and forging machines, an arrangement as claimed in claim 2 and fwhich includes, for actuating the electromagnetically controlled contacts, a single stroke a cam-adapted to break the electromagnetic circuit after each stroke, and a continuous operation control cam, adapted tolhold .thecontacts closed. after thegelectromagneticlcircuitlhasbeen bioli'en, use; the rarifa m'qii lhesiits uppermost position.

" JOHN 7 REFERENCES mm The following references are of record in the file of this patent:

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