US 3381672 A
Description (OCR text may contain errors)
May 7, 1968 Filed A brii 4, 1966 COMPRE55EQ AIR SUPPLY United States Patent 3,381,672 EMPULSE FORMING AND LIKE MACHINES Stephen Albert Tobias and Farhang Bakhtar, Birmingham, England, assignors to National Research Development Corporation, London, England, a British corporation Filed Apr. 4, 1966, Ser. No. 540,086 Claims priority, application Great Britain, Apr. 6, 1965,
14,613/65 2 Claims. (Cl. 123-46) ABSTRACT OF THE DISCLOSURE In an impulse forming machine in which the release of chemical energy in an energy chamber causes an impulse of a piston/cylinder combination to overcome a backing pressure of compressed gas and to impulse the forming dye of the machine, use is made of the impulse stroke to further compress the gas within the cylinder and a valve is provided to permit the charging of a storage system with the super compressed gas within the cylinder. The gas stored within the storage system is then employed to charge the energy chamber for subsequent impulse strokes.
This invention relates to impulse forming, forging or like machines.
In the specification accompanying patent application No. 408,959, now Patent Number 3,253,399 is described such a machine in which use is made of the energy of combustion of a fuel to provide at least part of the energy for the initiation of movement and/ or full movement of a part, hereinafter called the ram, of the machine that is impulsed to deform a workpiece by impact therewith. Usually in such machines, part of a die form will be attached to the ram and the shaping of the workpiece by the die is attained solely by virtue of the high velocity of the ram at impact.
The ram will normally be attached to a piston which is adapted to slide in a cylinder and the cylinder head will comprise a combustion chamber, the power stroke of the piston being caused by expansion of a combusting mixture of air and fuel which is injected into the chamher. The return stroke of the ram will be accomplished by pressurising the underside of the piston from a supply of compressed gas which will usually be air and which will usually be used to charge the combustion chamber. comparatively low air pressure will be needed to maintain the piston against the combustion chamber orifice while the compressed combustion chamber is being swept clear of the products of combustion and is recharged with fresh air and fuel; the charging pressure may be greater than that of the low pressure air without breaking a seal between the piston and the combustion chamber orifice because the cross-sectional area of the orifice will always be smaller than that of the cylinder.
With this system, some of the energy developed due to combustion is necessarily spent in overcoming the pressure of the low pressure air in the cylinder but as has been described in the specification of the aforementioned pending application, this is advantageous in providing for rapid acceleration of the piston and, in consequence, the ram, as the seal of the piston with the combustion chamber breaks. Unless, however, arrangements are made to relieve the pressure behind the piston its movement will simply lead to further pressurisation of the air and undue loss of energy in the ram. In the prior specification it was proposed that the space behind the piston should be vented to atmosphere through a relief valve, but it could equally be arranged to vent the space to atmosphere be suitable porting arrangements as for instance in the shaft joining the piston to the ram. The disadvantage of the former arrangement would be that there is a positive loss of energy in the ram and in the latter that the piston could not be returned to the firing position, simply by use of the low pressure air.
The present invention arises out of an appreciation of the fact that, although some energy of the ram may be lost by this over-compression of the low pressure air, the over-compressed air may be used to advantage in operating the machine.
According to the invention, the over-compressed air is used directly, or indirectly, in the charging of the combustion chamber so as to increase the working energy of the ram. In this way it is estimated that, in a typical case, the available power in the ram could be increased at least by 70 percent.
One arrangement of forming machine embodying the invention is illustrated, somewhat diagrammatically, in the accompanying drawing.
The machine comprises a ram 1 that is connected to a driving piston 3 by a shaft 2 which operates in a bearing 7 in plate 6, the bearing being sealed at 8. The piston is arranged to slide in cylinder 4 and, in the pro-firing position, is held against the head 5 by low pressure air in the cylinder 25, so as to seal the combustion chamber orifice by means of a plug portion attached to the piston.
The combustion chamber 9 is completed by a finned member 10 having an exhaust valve 11 and inlet valve 12 therein. Fuel is injected into the chamber by means of an atomiser 13.
Spaced bolts, such as visible at 15, serve to clamp the parts together to withstand the explosive and impacting forces, the parts 16 and 17 of the forming die being fixed to the ram 1 and base 18 respectively, columns 19 serving to space the plate 6 from the base.
In operation, low pressure air, say at p.s.i.g. is introduced through valve 26 to the space 25 beneath the piston 3. Vent valve 14 and exhaust valve 11 are opened at this stage to relieve the space above the piston and to permit exhaustion of the combustion products from the combustion chamber. When the piston has reached its upper limit in the cylinder and has sealed the combustion chamber orifice, the pressure in the space 25 attains that of the low pressure supply.
Thereupon the inlet valve 12 is opened to admit air from the accumulator 24, with valve 11 still open to permit the chamber 9 to be scavenged. Upon closure of the valve 11, the combustion chamber becomes charged with air at the pressure of that within the accumulator 24 which, as will be understood from the description below, is maintained at a higher pressure than that of the low pressure supply. Petrol is injected, by means of the atomiser 13, while air flow into the chamber continues and the petrol and air charges are well mixed in consequence. Valve 12 is then closed, followed by closure of valves 14 and 26, and the fuel/ air mixture is ignited by means of a sparking plug 21.
Ignition results in a rapid rise of pressure in the combustion chamber and the back-pressure due to the low pressure air in the space 25 is overcome, so that the seal at the orifice of the combustion chamber is broken with the result that the high pressure is immediately applied to the full area of the piston which then rapidly accelerates and moves the ram downwardly along its impacting stroke.
Since valves 23 and 26 are closed, the downward movement of the ram is accompanied by rise of pressure in the space 25 above the pressure of the low pressure supply. When this pressure has attained a predetermined value, which will be the pressure at which it is desired Patented May 7, 1968 to maintain the air in the accumulator 24, valve 23 is opened and the over-compressed air is delivered to the accumulator during the remainder of the stroke of the piston. As soon as the delivery operation is complete, valve 23 is closed though it may be arranged that the valve is closed at a pre-determined part of the stroke of the ram, but enables a greater amount of residual compressed air to remain in the space 25 to act as a cushion for the piston, and therefore for the ram.
To return the ram to its original position, valves 11 and 14 are opened and, with the compressed air acting behind the piston, the latter moves upwardly expelling the combustion products from the cylinder and the combustion chamber. Expansion of the residual over-compressed air in the space 25 causes the pressure to drop and, when it has reached the pressure of the low pressure supply, the inlet valve 26 is opened to force the piston to the upper end of its stroke whence the cycle of operations described above can be repeated.
It is to be observed, therefore, that the piston and cylinder arrangement is acting, in effect, as a compressor, drawing air into the cylinder during the return stroke of the piston and over-compressing it and delivering it to the accumulator, on the firing stroke. With the energy for impact being greatly dependent on the pressure at which the combustion chamber is charged, the use of a piston for boosting the air supply pressure for the combustion chamber results in a considerable increase of machine output.
As disclosed in the specification of the prior pending application referred to above, modifications to the machine may be made within then spirit of the invention, as will be understood by those skilled in the art. Thus the machine may be made double-ended and firing mechanism provided for both rams, in which case use may possibly be made of the invention described in the specification accompanying co-pending patent application No. 408,931, now Patent Number 3,329,003.
Operation of the machine described above may conveniently be arranged to be rendered automatic by use of a control device in accordance with the invention disclosed in the specification accompanying co-pending patent application No. 408,959; suitable electromagnetic actuating mechanism would then be necessary for the various valves and controls.
1. An impulse machine comprising a cylinder, a piston for said cylinder, an energy chamber for said piston and cylinder combination, said energy chamber having access to said cylinder towards one end thereof and to one side of said piston, an end wall disposed at the other end of said cylinder, a sliding ram member, said ram member having a shaft connecting to said piston, said shaft passing through said end Wall, inlet valve means arranged to give access to said cylinder towards the end thereof associated with said end wall, means for connecting said inlet valve to a source of compressed gas, said inlet valve means being adapted to provide access for compressed gas from said source through said connection to said cylinder whereby said piston may be forced against said energy chamber, outlet valve means associated with said cylinder in the region of said end wall, said outlet valve means being arranged to permit of high pressure gas being built up against said end wall during the impulsive stroke of said piston, a high pressure system, means connecting said high pressure system to said outlet valve means for permitting the charging of said storage system during the impulsive stroke of said piston, and a high pressure connection between said high pressure system and said energy chamber, -valve means in said high pressure connection, said high pressure connection valve means being arranged to provide access for high pressure gas from said high pressure system to said energy chamber, whereby said energy chamber may be charged with gas from said high pressure system for the release of chemical energy in said energy chamber.
2. An impulse machine comprising, an impulsed part, a piston member and cylinder therefore, said impulsed part being adapted to move under the influence of said piston member, an energy chamber for said cylinder, said energy chamber having access to said cylinder towards one end thereof and to one side of said piston, an upper plate and a lower plate for said cylinder, said energy chamber being associated with said upper plate and a relief valve for said cylinder in said upper plate, seating means on said upper plate adapted to co-operate with said piston member, inlet valve means associated with said lower plate for the supply of low pressure gas to the underside of said piston member for effecting a return stroke thereof, and to force said piston against said seating, high pressure outlet valve means associated with said lower plate, a high pressure gas system a connection between said high pressure gas system and said outlet valve means, a connection between said high pressure system and said energy chamber and valve means in said connection to said energy chamber to enable high pressure gas to be supplied from said system to said energy chamher for the release of chemical energy in said energy chamber.
References Cited UNITED STATES PATENTS 2,072,266 3/1937 Kiecksee 123-46 2,110,754 3/1938 Alston W 123-74 2,755,783 7/1956 Kupka 123--46 2,792,816 5/1957 Oyer 123-46 X 2,950,705 8/1960 Kuhn 123-46 X FOREIGN PATENTS 112,095 10/ 1944 Sweden.
WENDELL E. BURNS, Primary Examiner.