GB2241664A

GB2241664A - Power press

Info

Publication number: GB2241664A
Application number: GB8926541A
Authority: GB
Inventors: Anthony Baker; Alan Johnson
Original assignee: HILLTOP SECTIONS Ltd
Current assignee: HILLTOP SECTIONS Ltd
Priority date: 1989-11-24
Filing date: 1989-11-24
Publication date: 1991-09-11
Anticipated expiration: 2009-11-24
Also published as: GB8926541D0; GB2241664B

Abstract

Power press has a tool carrier driven through positive or substantially non-slip transmission means preferably providing a substantial stepdown drive ratio, by an electric servo-motor operable by stepping control in positively defined increments of movement for fine and consistent control of operation of the tool carrier and braking thereof resisting displacement when movement ceases.

Description

POWER PRESS This invention relates to power presses as used, for example, in the cutting and/or shaping of metal components and has as its object the provision of a power press which is particularly reliably and accurately controlled with substantial economies in energy requirements and simple and durable construction.

According to the invention there is provided a power press comprising a tool carrier movable from a position of rest to an acting position at which a tool formation of or on the carrier in use co-acts with a workpiece to effect an operation thereon, a power source, and transmission means connecting said source to the tool carrier for selectively effecting positive movement of the latter between said positions; characterized in that the power source is an electrically powered servo-motor operable by stepping control in positively defined increments of movement with a braking effect resisting displacement when movement ceases whereby the positioning and movement of the tool carrier is selectively controlled in a precise and positive manner.

Said transmission means preferably includes step down gearing, for example a substantially non-slipping belt and pulley drive whereby each said increment of movement of the motor results in a much smaller and therefore more finely controlled increment of movement of the tool carrier.

Said stepped down arrangement further ensures that the braking effect of the motor is multiplied in its application to the tool carrier, and that the power applied by the motor for driving the tool carrier is likewise multiplied.

In a typical example of the invention a power press having a reciprocating tool carrier driven by connection to a rotating crankshaft of the press in known manner is provided with a large diameter pulley on said crankshaft.

An electrically powered servo-motor is mounted at a convenient location, e.g. on a frame of the press with a small diameter pulley on its output shaft linked to the crankshaft pulley by a slip resistant belt, or possibly some other form of drive transmission e.g. a sprocket chain, toothed belt, or in some applications toothed gearwheels. In this particular example the step down ratio between the motor shaft and the crankshaft is 8:1.

The servo-motor is so constructed and controlled that it can be operated in a stepping manner in positively defined increments of movement each of which is a very small angular displacement of its output shaft, in one example one revolution of said shaft is subdivided into 2000 equal pulses or increments of angular displacement though this number may vary depending on the pattern of servo-motor utilized. The motor can be started or stopped on any predetermined pulse or increment so that very precise control is possible.

Moreover, when the motor is at rest under operating conditions it provides a braking effect resisting displacement from the angular position at which it stopped, this braking effect being provided with the use of very little energy. As this braking effect is substantially multiplied by the step down ratio between the motor shaft and the tool carrier the latter is positively retained at any predetermined position when the motor stopped with very high precision.

There is substantial saving in energy because there is no need for a continuously running large and heavy flywheel. The large pulley on the crankshaft itself provides sufficient flywheel effect for smooth operation during each cycle, and the motor and pulleys are not running except when actual movement of the tool carrier is required.

There are no moving parts such as idling drive trains or motors in between the operating and return strokes of the tool carrier so that wear and tear is substantially reduced and there is increased operating safety. Due to the few moving parts and the low stress under which they operate maintenance requirements are also substantially reduced. The tool carrier is always accurately and positively positioned at the selected rest position ready to commence the next operating cycle so that consistent and accurately timed operation is ensured with substantially no variation between successive operating cycles even over long term periods of production.

Claims

1. A power press comprising a tool carrier movable from a position of rest to an acting position at which a tool formation of or on the carrier in use co-acts with a workpiece to effect an operation thereon, a power-source, and transmission means connecting said source to the tool carrier for selectively effecting positive movement of the latter between said positions; characterized in that the power source is an electrically powered servo-motor operable by stepping control in positively defined increments of movement with a braking effect resisting displacement when movement ceases whereby the positioning and movement of the tool carrier is selectively controlled in a precise and positive manner.

2. A press as in Claim 1 wherein the transmission means includes stepdown gearing whereby each said increment of movement of the motor results in a much smaller positive increment of movement of the tool carrier.

3. A press as in Claim 2 wherein the stepdown gearing comprises a substantially non-slipping belt and pulley drive.

4. A press as in Claim 2 or 3 wherein the stepdown ratio between an output shaft of the motor and a crankshaft connected to reciprocate the tool carrier is B:1

5. A press as in any preceding claim wherein the servomotor is operable in a stepping manner in positively defined increments of movement each of which is a very small angular displacement of its output shaft.

6. A press as in Claim 5 wherein each said increment of movement is 1/2000 of one revolution of said shaft.

7. A power press substantially as hereinbefore described.