GB2069390A - Striker starting mechanism for hydrodynamic units - Google Patents

Abstract

The striker 3 in a pneumatic percussion device or a hydrodynamic stamping unit is accelerated to (in the unit) impact against liquid (not shown) and produce pulsed pressure by a mechanism comprises a compressed gas receiver 1, a shaft 2 in which the striker 3 is driven, and two cylinders arranged in series one after the other, namely, a control cylinder 5 and working cylinder 4 having, respectively, pistons 7 and 6 and said pistons are interconnected with last motion by means of rod 8. The working cylinder 4 is mounted in the receiver 1 such as to define a circular space 15 between the end of the working cylinder 4 and the end of the shaft 2 which space 15 communicates with the space of the receiver 1. Fluid supplied through a channel 13 raises piston 7 which after the last motion lifts piston 6 which is then blown upwards by gas pressure in the receiver 1 to rapidly open port 22 for accelerating the striker. <IMAGE>

Description

SPECIFICATION Striker starting mechanism for hydrodynamic units The present invention relates to devices for hydrodynamic stamping and, more particularly, it relates to striker starting mechanisms of hydrodynamic units, The present invention can be used most advantageously for developing striker starting means in hydrodynamic presses providing for full opening of the valve prior to starting the striker acceleration.

This invention can be also used for developing pneumatic percussion devices.

There are known in the art devices for hydrodynamic stamping equipped with striker starting mechanism of different designs, said mechanisms serving for injecting compressed gas to the above-striker space of the cylinder for the striker to accelerate and accumulate kinetic energy which turns to pulsed pressure upon the striker impact against liquid.

Prior art devices face a problem of rapid opening of passages communicating the compressed gas receiver with the above-striker space of the cylinder, such that the striker should be accelerated by a gas pressure close to that in the receiver with a view to reducing the losses in the energy of compressed gas when throttling the latter through an opening port of the starting device.

There are also known in the art devices for hydrodynamic stamping wherein the starting mechanism (means for feeding compressed gas into the above-striker space of the shaft) is fashioned in the form of a system of slide valves, with the main valve which includes a gate and a spring affecting the latter being arranged on a conduit which communicates the receiver with the above-striker space of the cylinder. An additional distributor of the compressed gas supply, comprising a spring, is mounted at the side of the main valve and has a small-diameter piston, a slider and a large-diameter piston made integral with an axial control rod extending inside the cylinder. The additional distributor communicates via channels with the above-striker space of the cylinder and with the channel for the supply of air to said space.The additional distributor also has an outlet port and a series of conduits and openings (cf., French Patent No. 2,138,378, IPC B 21 D 26/00).

Further known in the art is a striker starting mechanism in a device for treating materials (cf., U.S. Patent No. 1.562.426, class 72-430. of 1 965). comprising three axially aligned cylinders with pistons located therein for reciprocation. The two main cylinders. namely, a large-diameter top cylinder and a smail-diameter bottom cylinder. are interconnected with the aid of flanges. A series of circumferentially arranged ports are provided in the body of the bottom cylinder The working piston housed therein provides a means for opening the ports to let compressed gas from the receiver to the above-striker space of the shaft and for subsequently closing said ports.The other piston located in the large-diameter top cylinder serves a means for controlling the first, working cylinder and makes the latter move in response to an appropriate external signal. At the same time, the top cylinder serves a receiver of compressed gas used for accelerating the striker. Both pistons are rigidly interconnected by means of a rod and form a slide. The return of the slide to the initial position is effected by means of an additional, third cylinder formed by a central bore in the rod.

A support rod on which the slide moves is immovably mounted on the lower flange of the working cylinder. The supply of gas for returning the slide to the initial position is effected via passage provided in the body of the support rod.

In the initial position, both pistons are urged against the respective end seals by the resultant force of gas pressure against the various areas of the piston surface. A rigid connection of the working and control pistons serves to increase the inertial mass of the slide and, therefore, in the design provision is made for a certain distance between the initial position of the working piston and the upper edge of the outlet ports, through which distance the slide is accelerated at a rate sufficient to ensure the shortest time of transition from fully closed ports to fully opened ones and an abrupt ejection of compressed gas to the abovestriker space of the shaft.However, the provision of such distance, combined with the working piston stroke along the outlet ports, results in the formation of a "parasite" volume in which the compressed gas from the receiver expands and releases energy without performing any useful work. Since the bottom cylinder is arranged structurally inside the shaft in the top portion thereof, the "parasite" volume may reach considerable size.

Said prior art striker starting mechanism operates in the following manner.

Compressed gas filling the space of the control cylinder acts upon the inner end surfaces of the control and working pistons and, owing to the difference in their areas, urges the slide against elastic seals while maintaining it in unstable equilibrium. When the cylinder space comes in communication with the gap provided between the control cylinder lid and control piston, the equilibrium is disturbed, the pressure acting upon the inner end face of the control piston is cancelled by the pressure acting upon the outer end of said piston, and the pressure acting upon the inner end of the working piston starts moving the slide and withdrawing it from the seal.After the slide is displaced and withdrawn from the sea is. the gas from the receiver rushes through a plurality ot openings provided over the periphery of the control piston and fully balances the pressure on the opposite surfaces of the control piston. As a result. the slide moves at a very hlgn acceleration rate under the effect of the force developed by the pressure of gas against the working piston and acquires a high velocity bv the time it reaches the ports. The release of gas to the above-striker space of the working cylinder occurs over a very short period of time.

At the end of the stroke the slide is braked and displaces the liquid from the lower portion of the seat of the working piston cylinder. The slide is returned to the initial position by the gas supplied from the source along the support passage.

The afore-described prior art mechanism suffers from a series of disadvantages, primarily: ~the complexity of design due to the presence of three piston-cylinder pairs for opening the outlet ports and returning the slide to the initial position, the need for a strictly coaxial arrangement of said pairs rendering the structure rather inefficient and placing most stringent requirements upon the accuracy of manufacture of both single elements and the structure in general; ~high accelerations upon starting and, in particular, upon stopping the slide, cause enormous stresses therein, which calls for the use of highly strong and lightweight materials for its manufacture, however, the service life of the striker is rather insufficient even if said conditions are met:: - a low efficiency figure due to the presence of a structurally essential large "parasite" volume between the working piston of the mechanism and the striker, as well as due to losses caused by the fact that the gas passed through the plurality of openings in the control piston will not take part in accelerating the striker.

It is an object of the present invention to eliminate the abovementioned disadvantages.

The main object of the present invention is to develop a striker starting mechanism for a hydrodynamic unit, which would help considerably simplify the design of the unit and improve the efficiency of the hydrodynamic unit due to an original accomplishment of the working cylinder.

Said object is attained through the use of a mechanism for starting a striker for accelerating the latter in the shaft of a hydrodynamic unit, having a compressed gas receiver and two cylinders arranged in a series one after the other, namely, a control cylinder and a working cylinder, whose pistons are interconnected by means of a rod, the piston of the control cylinder being acted upon by a compressed medium which sets said piston in motion and acts via the rod to move the piston of the working cylinder, in which mechanism, according to the invention, the working cylinder is mounted in the receiver such as to define a circular space between the end of said cylinder and the end of the shaft, said space communicating with the space of the receiver while the piston of said cylinder is mounted for movement relative to the rod.

Such an arrangement makes for a possibility of increasing the efficiency of the unit thanks to an increased speed of response of the unit by reducing tne inertial mass of the working cylinder piston. Upon separation of said piston from the end seal located on the end of the shaft, compressed gas supplied to the space between the working cylinder piston and the striker accelerates only the working cylinder piston for full opening of the inlet port thanks to the absence of rigid coupling between the rod and piston of the control cylinder. In addition, the circular space reduces the path of compressed gas from the receiver to the outlet port of the shaft and, consequently, energy losses along said path.

The absence of rigid coupling between the rod and piston of the working cylinder makes for a simpler structure and for lower requirements placed upon the accuracy of manufacture of both individual parts and the entire mechanism inasmuch as no axial alignment of the control and working cylinders is required in this case.

The herein disclosed mechanism design helps practically eliminate the "parasite" volume, whereby the efficiency of compressed gas energy is sharply increased. A decrease of the mass of the working piston as compared with that of the prototype slide and the reduction of the acceleration path help considerably reduce the loads in the piston of the working cylinder, thereby lowering the requirements upon the piston material and extending the service life of the overall mechanism.

It is expedient that the piston of the working cylinder be made hollow and accommodate thereinside a stop secured on the rod and acting upon said piston in order to communicate the receiver space with the shaft space upon starting the striker and to close said spaces upon return of the striker to the initial position.

Such an arrangement helps further improve the speed of response thanks to reducing the mass of the working cylinder piston and simplify the overall mechanism.

It is also expedient to communicate the space between the striker and bottom piston with the atmosphere by means of a passage provided in the receiver body.

The provision of said passage guarantees from spontaneous operation of the starting mechanism due to possible leakage of compressed gas through the end seal.

The present invention will be more apparent upon considering the following detailed description of an exemplary embodiment thereof with due reference to the accompanying drawing which shows a general view of the mechanism for starting a striker for accelerating the latter in the shaft of a hydrodynamic unit, according to the invention, a fragmentary longitudinal sectional view of the striker starting mechanism of a hydrodynamic unit.

Disclosure is made of a mechanism for starting a striker for accelerating the latter in the shaft of a hydrodynamic unit, which comprises a compressed gas receiver 1 enveloping a shaft 2 of the hydrodynamic unit with a striker 3 movable therein. The starting mechanism further comprises a working cylinder 4 and a control cylinder 5. said cylinder arranqed in series one after the other and having a working piston 6 and a control piston 7.

respectively. The pistons 6 and 7 are interconnected by means of a rod 8. The control cylinder 5 is covered with a lid 9 having a channel 10 for the supply of compressed medium to a piston space 11. Compressed medium is supplied to a rod space 12 of the control cylinder 5 via channel 13. The cylinders 4 and 5 are mounted in a lid 14 closing the spaces of the receiver 1 and shaft 2, the working cylinder 4 being mounted such as to define a circular space 1 5 between the receiver end and the end of the shaft 2, said space communicating with the space of the receiver 1 via passages 16. The piston 6 of the working cylinder 4 is mounted for movement relative to the rod 8 on whose end there is provided a stop 17 acting upon the piston 6 during the mechanism operation. In the initial position, the piston 6 is urged against a seal 18.In order to reduce the stresses occurring in the piston 6 upon braking, provision is made of an absorber 19. For precluding spontaneous starting of the striker due to the leakage of compressed gas via the seal 18, a passage 20 is provided in the lid 14 of the receiver 1, said passage housing a controlled valve 21 opening when the working piston 6 closes an inlet port 22 of the shaft 2 and closing prior to opening of said port.

The herein disclosed striker starting mechanism of a hydrodynamic unit operates in the following manner.

Shown in the drawing is the moment when the working piston 6 is urged against the seal 18 by the force of the control cylinder and pressure of compressed gas in the circular space 15. While so doing, the valve 21 is open and the space between the striker 3 and working piston 6 communicates with the atmosphere by means of the passage 20.

For starting the striker, i.e., for communicating the receiver 1 with the above-striker space of the shaft 2, compressed medium is supplied to the rod space 12 of the control cylinder 5 via the channel 13, and the piston 7 together with the rod 8 and the stop 17 start moving upwards. Upon said movement, the valve 21 closes. The stop 17 moving upwards reaches the flange of the working cylinder 4 and separates the latter from the seal 18 whereupon the compressed gas moves into the space between the working piston 6 and the striker 3 to affect the ends of the latter and accelerate them in the opposite directions.

Since the mass of the piston 6 is 10-20 times smaller than that of the striker 3, the latter will move through 1-2 mmfrom its initial position by the time the working piston 6 reaches the absorber 1 9 and opens the inlet port 22 of the shaft 2 fully, and entire stage of acceleration of the striker 3 by compressed gas will take place with the passages 16 and port 22 fully opened, this eliminating the losses of compressed gas energy for throttling.

After a preset volume of compressed gas has been passed over to the above-striker space of the shaft 2, the compressed medium is supplied via channel 10 to the piston space 1 1 of the control cylinder 5. The piston 7 with the rod 8 and stop 17 move downwards to urge the working piston 6 against the seal 18 and disconnect the receiver 1 from the above-striker space of the shaft 2, whereby the valve 21 opens to reduce the pressure in the space between the striker 3 and working piston 6 down to atmospheric pressure.

Thanks to such an arrangement, the starting mechanism according to the invention is simple of design and requires no special materials and complicated techniques for its manufacture, whereby its cost is reduced considerably. The absence of "parasite" volumes and high speed of response make for a much higher efficiency of the hydrodynamic unit.

Claims (4)

1. A striker starting mechanism of a hydrodynamic unit, comprising: a shaft wherein said striker is movable; a compressed gas receiver; two cylinders with pistons, namely, a control cylinder and a working cylinder, arranged in series one after the other; said working cylinder mounted in said receiver; a circular space defined by the end of said working cylinder and the end of said shaft and communicated with the space of said receiver; a rod adapted to interconnect the pistons of said cylinders; the piston of said working cylinder mounted for movement relative to said rod; a compressed medium acting upon the piston of said control cylinder to set said piston in motion and, via said rod, acting upon the piston of said working cylinder.

2. A striker starting mechanism as set forth in claim 1, wherein the piston of said working cylinder is made hollow and accommodates thereinside a stop secured on said rod and acting upon said working piston in order to communicate the space of said receiver with the space of said shaft upon starting the striker and to close said spaces upon the return of said striker to the initial position.

3. A striker starting mechanism as set forth in claim 1, wherein the subpiston space of said working cylinder communicates with the atmosphere by means of a passage provided in the body of said receiver.

4. A striker starting mechanism of a hydrodynamic unit substantially as hereinabove described with reference to and as shown in the accompanying drawing.