Presses – Methods
Reexamination Certificate
1999-04-09
2001-03-27
Vo, Peter (Department: 3721)
Presses
Methods
C100S048000, C100S269140
Reexamination Certificate
active
06205916
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a stamping press, preferably a desk-top stamping press. The press can be used for a variety of stamping functions, among which are embossing a substrate, applying a foil to a substrate or applying foil and an emboss to a substrate. The invention is particularly, but not exclusively, useful for applying security markings to documents.
BACKGROUND OF THE INVENTION
Foil embossing machines are conventionally substantial pieces of equipment located in a factory or printing shop environment. However there is a need, particularly for the preparation of important documents such as passports and cheques, for the security features to be applied locally and on a one-off basis to a document. This need could be satisfied by a desk-top foil embossing machine, and it is therefore an object of this invention to provide a stamping press which can be used on an intermittent basis, from a desk-top location in an office environment.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a method of operating a stamping press which has a pair of plates defining a press gap between them, and an hydraulic ram to produce relative movement between the plates to close the press gap and apply pressure to the die to press the die against a substrate in the gap, wherein the hydraulic ram is fed with hydraulic fluid from a pump driven by an electric motor, the method comprising the steps of driving the motor to pressurize the hydraulic system to a pressure below the maximum pressure to be achieved, shutting off electric current to the motor and allowing the motor to continue to run under its own inertia until it stalls, to pressurize the hydraulic system to a higher pressure, and opening a valve to dump the pressure after a predetermined time period.
The motor may be shut off in response to the attainment of a specific predetermined pressure in the system, eg in response to a signal from a pressure sensor, or it may be shut off after a specified time which has been predetermined as corresponding to a desired pressure in the hydraulic system. As an alternative to the use of a conventional pressure sensor, electric current drawn by the motor may be measured. A rise in current corresponds to attainment of a particular pressure.
The press may be operated so that when the pressure in the hydraulic system reaches the predetermined low pressure, a first timer is started and after a pre-set time period electric current to the motor is switched off. A second timer can be used to determine when the dump valve is opened to dump the pressure.
The motor may have a flywheel and the size of the flywheel will then be determined in accordance with the maximum pressure to be achieved. Alternatively, the mass of the motor rotor may provide sufficient inertia for a separate flywheel to be unnecessary.
The invention further provides a stamping press which has a pair of plates defining a press gap between them, an hydraulic ram to produce relative movement between the plates to close the press gap and apply pressure to the die to press the die against a substrate in the gap, a hydraulic pump driven by an electric motor through a flywheel, means for shutting off the motor on reaching a predetermined pressure in the circuit, and a dump valve for dumping hydraulic pressure from the circuit.
The press is preferably adapted to be placed on a table for operation. The press may have a manual feed by which an operator can feed single substrates into the press. In some embodiments, where continuous stationary is to be embossed, a conventional tractor feed can be used to feed substrate through the press.
The press preferably is powered by an electricity supply available in an office environment, and preferably the power consumption of the press is less than 1500 W. This is well within the limits of standard office power supplies.
A typical press-in accordance with the invention has a motor rated at 150 watts, with a heater rated at 350 watts.
One of the plates is preferably fixed and the other is movable to close the press gap. The gap will normally be horizontal, and either the upper or the lower plate can be the movable plate.
The hydraulic pump and the electric motor can be housed in a reservoir of hydraulic fluid, so that the fluid acts as a coolant for the motor. A fan can be provided to cool the exterior of the reservoir, to extract heat from the fluid therein.
Using such a press makes it possible to apply the extremely high pressures required for embossing fine foiled patterns on substrates. For example, a press with a 150 watt motor can apply a total load of up to 10 tons. Hot stamping dies require a pressure of 2-3 tons/in
2
, so the pressure attainable by this press, with its small overall size, is quite suitable for such purposes. In the case of applying a foil without any embossing, lower pressures are required, and the press can apply foil to a complete A5 sheet in one pass, and thus a complete A4 sheet in only two repeat impressions.
According to a second aspect of the invention, there is provided a stamping press having a pair of plates defining a press gap between them, at least one of the plates being adapted to carry a stamping die, a foil feed and take off arrangement adapted to feed foil to one side of the gap and to draw foil off from the other side of the gap, and an hydraulic ram to produce relative movement between the plates to close the press gap and apply pressure to the die to press the die against the foil and the foil against a substrate in the gap, wherein the foil feed and take off rollers are mounted above the ram and the foil is fed from the take-off roller, substantially parallel to the ram actuation direction towards the gap, and from the gap again in a direction substantially parallel to the ram actuation direction to a take up roller.
The stamping die can, for example, be a foiling die, an embossing die or a foil/emboss die.
By thus locating the ram inside the foil path, a machine with a very small footprint can be achieved, making the machine suitable for desk-top use.
The stamping die can preferably be removed and replaced from one side of the press, without dismantling other components. The die can be mounted on a plate which slides in guide tracks on one of the press plates, and a locking mechanism can be provided to secure the die plate in position.
The foil feed and take off arrangement is preferably mounted wholly within the area of the press platen projected in a direction parallel to the axis of the ram.
The hydraulic ram is preferably included in a hydraulic circuit comprising a pump, a pressure sensor and a fluid reservoir, wherein the pump is driven by an electric motor through a flywheel.
One of the press plates preferably moves with the hydraulic ram and the other is non-moving. The fluid reservoir may be incorporated in the non-moving plate of the press.
According to a third aspect of the invention, there is provided a foil feed arrangement in a foiling press, the arrangement comprising an undriven set of rollers on the upstream side of the press and a driven set of rollers on the downstream side, the driven set comprising a relatively small diameter roller and a relatively large diameter roller, the two rollers being mounted parallel and in contact with one another to define a foil nip, a motor arranged to drive the smaller of the rollers, foil guide surfaces arranged to feed foil from the press around at least 180° of arc on the larger roller, into the nip and around the smaller roller to a take-up reel.
The drive motor is preferably a stepper motor or a synchronous motor with the drive motor spindle mounted on the axis of the smaller roller, to give a direct drive. The smaller diameter roller can have a friction-enhancing surface.
REFERENCES:
patent: 2614539 (1952-10-01), Ernst
patent: 4151718 (1979-05-01), Gravely, Sr.
patent: 4264394 (1981-04-01), Izumihara
patent: 4707988 (1987-11-01), Palmers
patent: 5134931 (1992-08-01), Thompson et al.
patent: 5158723 (1992-10-01), Walchhutter et al.
patent: 5
Blackfoil Group Limited
Bourque & Associates PA
Huynh Louis K.
Vo Peter
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