FI74637C - Device at a pressure medium driven impact apparatus for controlling the stroke of an impact piston. - Google Patents

Description

74637

The present invention relates to an arrangement for a pressure medium driven percussion device for adjusting the stroke length of a percussion piston, comprising - a body with a housing for the tool and a percussion cylinder when it is in the housing in the impact position, - a pressure medium-filled cushion cylinder facing the impact cylinder for stopping the impact piston, and 15 - a source of pressure medium connected to the impact cylinder in the cylinder.

Hydraulic percussion devices have a pressurized fluid-operated flat cylinder formed on the tool-side end of the percussion cylinder, which is fixedly located in the body of the percussion device or in the percussion cylinder axially locked to the body. In known solutions, in a normal working position, the impact piston first strikes the end of the tool in the correct impact position in the tool housing, after which the impact piston returns to the opposite end of the impact cylinder for a new impact. If the tool has moved sufficiently forward from the normal impact position in the tool housing, the impact piston 30, with its full impact energy, strikes the pad cylinder, which brakes and stops the impact piston. In this situation, the length of the stroke increases compared to a normal working situation. Likewise, the is-kun length increases if the tool has moved slightly forward and is therefore not located at the correct point of impact.

Such a longer stroke of the percussion piston causes some essential disadvantages. The flow of high pressure fluid to the impact cylinder must be shut off before the impact piston is in the normal impact position and the impact cylinder connection to the 2 74637 tank must be opened so that the impact piston can return for a new impact. A longer stroke of the piston stopping in the cushion cylinder causes an increase in suction in the impact cylinder, so that the pressure of the liquid drops below the tank pressure, whereby cavitation may damage the parts of the impactor.

FI patent application 763159 discloses a hydraulic percussion machine in the body of which a damping piston is mounted, through which the tool extends and which keeps the tool at a certain minimum distance from the point of impact. During the effective working phase, the tool 10 is pressed against the frame, whereby the clearance is reduced to zero. The structure according to the publication does not solve the problem associated with a longer stroke length of the percussion piston during idling.

SE-A-395 126 discloses a nailing device 15 having a percussion cylinder in the body for an percussion piston. The smaller diameter lower part of the impact piston is surrounded by a brake sleeve which can move relative to the impact piston in the impact cylinder and which in its lower position presses against the sleeve attached to the body. The brake sleeve dampens the final movement of the impact piston when the larger diameter base of the impact piston protrudes into the damping space in the brake sleeve, and the impact movement stops when the base of the shock piston contacts the bottom of the damping space. The device has an adjustable pressure relief system for adjusting the stroke intensity of the percussion piston, but the stroke length of the stroke-25 piston is not adjustable. In this device, too, the impact piston performs a longer idle stroke than when the impact piston performs a normal working stroke on the nail base.

U.S. Patent No. 3,608,650 discloses a punch having a cylinder bore in the body for a retaining piston through which a smaller diameter impact arm of an impact piston extends. The impact piston moves in an impact cylinder made in the frame. When a punch is used, the pressure medium is first introduced into the cylinder bore of the retaining piston to raise the retaining piston to place the product to be stamped under the Meis-35. The pressure medium is then introduced into the space between the impact piston and the retaining piston to bring the retaining piston into contact with the product. Finally, the pressure medium is introduced into the impact cylinder so that the impact piston moves downwards and strikes the die. The stroke length is not adjustable. The stroke length of the impact piston is limited in the upper position by the contact of the piston with the upper end of the impact cylinder and in the lower position by the contact with the upper surface of the retaining piston. The length of the idle stroke of the impact piston increases compared to a normal working stroke.

It is an object of the present invention to provide adapters for a pressure medium driven impact device which avoids the above disadvantages and which allows the stroke length of the percussion piston to be maintained at normal stroke even when the percussion piston performs idle strokes when the tool is out of impact and the piston stops. This object is achieved by an arrangement according to the invention, characterized in that the arrangement comprises means for connecting a cylinder acting as an adjusting cylinder to a pressure medium source so that the pad moves towards the percussion piston for adjusting the axial position of the pad piston to shorten the stroke length in the housing.

The invention is based on the idea that the pad cylinder, to which the impact piston stops when the impact piston performs 25 idling strokes, is moved axially against the direction of impact, i.e. towards the impact piston, when the tool is out of the impact position. In this way, the length of the idle stroke is shortened to the same length as the stroke of the percussion piston when the tool is in its impact position. Such displacement of the cushion cylinder 30 is accomplished by automatically displacing the cushion piston based on the position of the tool or the control obtained from the load on the impactor feed mechanism.

4 74637 4

The arrangement according to the invention achieves several advantages over known solutions: - shorter stroke length at idle, where a smaller low-pressure accumulator can be used and the risk of cavitation is reduced, - the possibility of using non-combustible liquids, - lower tank pressure and consequently higher pressure difference, efficiency lower impact velocity due to the stroke length, resulting in a shorter cushion cylinder and thus a shorter impact device, - when the impact piston strikes the cushion cylinder, the impact on the body is soft whereby the tool and the machine can be shortened, - the amount of pressure medium required is reduced due to the shortening of the stroke if the stroke rate remains constant.

The invention will be described in more detail below with reference to the accompanying drawings, in which Figures 1A and 1B show a hydraulic percussion device provided with an arrangement according to a first embodiment of the invention in axial section during a work stroke and an idle stroke, respectively. Fig. 2 shows a hydraulic percussion device according to a second embodiment. Figures 3A and 3B show a hydraulic impact device 30 provided with an arrangement according to a third embodiment in axial section during an idling stroke and a working stroke, respectively, and Fig. 4 shows a hydraulic percussion device with an axial section according to a fourth embodiment. during the attack.

Il 5 74637

In the embodiment shown in Figures 1A and 1B, the displacement of the cushion piston is based on the use of a separate pressure medium source and control of the displacement from the supply pressure of the feed cylinder of the drilling machine or the hydraulic motor of the feed mechanism.

5 The body 1 of a drilling machine has a housing 2 in which a tool 3 is slidably inserted axially. The body has an impact cylinder 4 coaxial with the housing for an axially movable impact piston 5. The tool housing end of the percussion cylinder abuts the pad piston 6, which moves axially with the percussion cylinder 10 in a coaxial adjusting cylinder 7. The pad piston is sleeve-like and surrounds the percussion piston rod 5a extending to the tool housing. The impact piston-side surface of the cushion piston has a cushioning cylinder 8 for the impact piston. The percussion cylinder is surrounded by an axially movable valve member 9 for alternately directing the pressure medium to different sides of the percussion piston. The body has an inlet passage 11 connected to the liquid pump 10 for conducting the pressure fluid to the impact cylinder and an outlet passage 13 connected to the tank 12 for removing the pressure fluid from the impact cylinder. The valve mechanism is of a type known per se, and its structure and operation are therefore not explained in more detail.

In order to move the drilling machine, a feed cylinder 14 is arranged, for example, fixed to the feed beam. The feed cylinder can also be replaced by a hydraulic feed motor of the chain feed mechanism or another similar pressure-fluid-fed feed mechanism. The supply cylinder is connected via a valve 15 to the liquid pump 16 and the tank. Using the valve causes the piston of the feed cylinder to push the drill forward or pull it back.

The control cylinder 7 is connected via a channel 17 in the body to a pressure-controlled control valve 18, which in turn is connected to a liquid pump 19 and a tank. The liquid pump is further connected via a pressure control valve 20 directly to the tank. The supply line 21 of the supply cylinder 14 is connected to the control valve 18 to control its operation.

6 74637

When the drilling machine is fed forward, the supply line 21 of the supply cylinder 14 has a supply pressure provided by the liquid pump 16. The supply pressure directs the valve 18 to a position where the control cylinder 7 in front of the cushion piston communicates with the tank 5, as shown in Fig. 1A. In this case, the fluid pressure acting on the impact cylinder behind the pillow piston pushes the pillow piston to its forward position, and the impact piston has the full stroke length. The impact piston then strikes the end of the tool in the impact position 10 in the housing 2, which stops the impact piston without the impact piston hitting the pad cylinder 8.

If for some reason the tool moves out of its impact position in the housing and thus does not resist the feed of the drilling machine, the pressure of the feed cylinder 14 and the supply line 21 will decrease.

In this case, the valve 18 moves to the position according to Fig. 1B, in which the pressure fluid of the liquid pump 19 can flow into the control cylinder 7. This causes the cushion piston to move towards the percussion piston, whereby the stroke length is shortened. When the drilling machine has moved so far forward that the tool is again in the impact position-20, the pressure in the feed cylinder and the supply line rises and directs the valve 18 back to its original position, allowing the pressure fluid to flow again from the control cylinder to the tank. The pressure control valve 20 allows the liquid pump 19 to flow into the tank when the pressure rises to a certain pre-set level 25, thus preventing the equipment from breaking.

Instead of a separate fluid pump 19 and associated equipment, the required pressure fluid can be taken, for example, from the pressure fluid going to the feed mechanism or from the pressure fluid going to the impact or rotation mechanism of the drilling machine.

30 The operation of the machine is exactly the same as when the tool is out of the impact position if the feed direction of the drilling machine is changed. This is based on the fact that when the direction of the supply is changed, the supply line 21 becomes an outlet line and the liquid pressure is lost, whereby the valve 18 is set in the position 35 according to Fig. 1B.

Il 7 74637

In the embodiment shown in Fig. 2, control is taken to move the cushion piston from the isupup pressure generated in the cushion cylinder.

The cushion piston 6 has a channel 22 5 leading to its outer circumference and the body has an outwardly leading channel 23 which is connected via a non-return valve 24 and a throttle 25 to a control valve 18 for controlling its operation. In this case, the valve 18 operates to release the liquid pressure control cylinder 7 of the liquid pump 19 when sufficient pressure is applied to the control channel of the valve.

In normal operation, the cushion piston is pushed into its foremost position and the valve 18 is in a position where the flow of pressure fluid to the control cylinder is blocked. As the tool moves out of its impact position, the impact piston strikes the blade 8 of the cushion-15, thereby damping the impact. At the same time, the impact causes an increase in pressure in the cushion cylinder, whereby the pressure fluid flows through the channel 22 in the cushion piston and the channel 23 in the body through the valve 24 to the control valve 18, causing its position to change. As a result, the pressure fluid 20 can flow into the control cylinder and move the cushion piston to the upper position shown in Fig. 2, i.e. to the rearmost position. If the tool remains out of its impact position, the impact piston strikes the pad cylinder with each stroke, whereby the valve 18 is constantly subjected to a sufficient pressure 25 and the pad piston remains in the up position.

When the tool returns to its impact position, the impact piston no longer strikes the padding cylinder sufficiently, so that the pressure acting on the valve 18 can be released through the choke 25 to the level of normal working pressure. As a result, the valve 30 18 changes its position, allowing the pressure fluid to flow from the control cylinder to the tank, whereby the working pressure acting on the percussion cylinder of the drilling machine pushes the cushion piston to its forward position for normal operation.

This solution also works when pulling the drill backwards 35, because the tool disengages from its impact position and the impact piston then strikes the pad cylinder.

s 74637

In the embodiment shown in Figures 3A and 3B, the movement of the cushion piston is controlled by a separate control piston.

At the end of the body tool housing 2 there is a guide cylinder 26 with an axially movable guide piston 27. The body 5 has a channel 28 which communicates with the guide cylinder and is connected by a line 29 connected via a check valve 30 and line 31 to a shock cylinder fluid pump 10 and a throttle 32 valve. 33 to control its operation and through the pressure control valve 34 to the tank-10.

The circumferential surface of the cushion piston has a slot 35 connected to the control cylinder 7 at the channel 22 and the body has a channel 36 leading to the channel 17 of the control cylinder at this slot.

Figure 3B shows the pad piston in a normal working position, with the tool in the housing in the impact position pressed against the guide piston 27.

The guide piston 27 is in contact with the end of the tool and moves towards the tool under the action of the fluid pressure acting on the guide cylinder 26 as the tool moves out of the is-20 position in the housing. As the steering piston moves forward, the pressure in line 29 decreases. When it has dropped to the same level as the pressure in the line 31 from the liquid pump 10, the non-return valve 30 opens, allowing the pressure fluid to flow from line 31 to line 29. This pressure is lower than the pressure normally present in line 29. The pressure-controlled valve 33 is adjusted so that its switching pressure is higher than the pressure in the line 31. In this case, when the pressure drops, the valve changes its position to the idling position shown in Fig. 3A, whereby the channel 17 leading from the cushion piston control cylinder 7 to the tank closes and the pressure fluid can no longer flow out.

As the impact piston now strikes the impact cushion, it causes the pressure fluid to flow through the passage 22 and the gap 35 and the passages 36 and 17 into the control cylinder. Since the area under pressure of the impact cushion-35 is much smaller than that of the cushion piston

II

9 74637 area facing the cylinder, the cushion piston moves with each stroke towards the percussion piston until it has moved to its rearmost position. The velocity of movement of the cushion piston towards the percussion piston increases as it is displaced, because the restrictive effect on the fluid flow of the gap 35 5 decreases as the flow distance shortens.

When the tool returns to the impact position, it pushes the control piston 27 to its upper position, whereby the control piston pushes the pressure fluid out of its way. Since the non-return valve 30 prevents the pressure-10 liquid from penetrating the line 31, the pressure in the line 29 rises and directs the pressure valve 33 to a position where the channel 17 coming from the control cylinder communicates with the tank. In this case, the pressure fluid can flow from the control cylinder to the tank, and the cushion piston can move to its lower position. The purpose of the pressure control valve 15 is to prevent the pressure in the line 29 from becoming too high. When the pressure has risen to the level of the valve setpoint, it allows unnecessary pressure fluid to flow into the tank.

A non-return valve can be installed in the duct 22, the opening pressure of which is higher than the working pressure of the impact cylinder 4, in order to prevent leakage from the duct 22 during normal working strokes.

Any small leaks past the control piston 27 do not affect the operation of the device, because the piston moves forward with each stroke 25, whereby more pressure fluid flows from the line 31 when the pressure drops too low. In order to prevent the valve 33 from reacting too quickly in such cases, a choke 32 can be installed in the valve control channel. At the same point, the choke can also be used to slow down the operation of the valve 33 anyway, so that the rate of change can be set as desired.

The embodiment shown in Fig. 4 corresponds to the embodiment according to Figs. 1A and 1B, but has the liquid pressure required to move the cushion piston taken from the fluid fluid pump 10 of the percussion cylinder via line 37. In this case, a pressure boosting device 38 can be connected to the pressure line 37, if necessary. as desired to its rear position.

The operation is controlled in the same way as in Figures IA and IB.

The drawings and the related explanation are only intended to illustrate the idea of the invention. The details of the arrangement according to the invention can vary considerably within the scope of the claims.

10 It is of course possible to combine different control methods and connections for directing the pressure fluid to the control cylinder. A practical alternative would be to combine the control piston structure shown in Figures 3A and 3B to control the control valves 18 shown in Figures 1A and 4 instead of the fluid pressure obtained from the supply device 10.

The solution according to the invention is applicable to different types of drilling and impacting machines. The sleeve-mounted cushion piston can be located on both the front and rear of the drill, thus adjusting the length of either the front or rear of the impact cylinder, respectively.

Il-

Claims (5)

An apparatus for a pressure medium driven impact apparatus for controlling the stroke length of the impact piston, comprising: an impactor (1) with a housing (2) for a tool (3) and an impact cylinder (4), - one in the impact cylinder axially back and forth movable impact piston (5) for subjecting the tool to impact when it is in a stroke position in the housing, - a pressure-mediated die cylinder (8) facing the impact cylinder to stop the impact piston, and - an impact member connected to the impact cylinder. a pressure medium source (10) for effecting the stroke of the stroke piston, and 15. an axial abutment piston (6) axially adjacent to the stroke cylinder (4), which moves axially towards and from the stroke piston (5) in a cylinder (7) between the body (1) and the die piston, characterized in that the device comprises means (18; 18, 22; 22, 27, 33) for connecting the cylinder (7) acting as a control cylinder to a pressure medium source (19; 10), so that the die piston (6) ) moves toward the impact piston (5) to adjust the axial position of the pad piston provide for shortening the stroke of the piston, where the tool (3) is in the housing (2) away from the stroke. 2. Device according to claim 1, wherein the impact apparatus is provided with a pressure medium driven feeding device (14) for feeding the body (1) in the axial direction of the impact piston (5), characterized in that the means for connecting the control cylinder (7) to the pressure medium source (19) is made up of a control valve (18) actuated by the pressure medium of the feeder device (14), which, when the supply pressure of the pressure medium in the feeder device exceeds a certain pressure, opens the discharge cylinder of the control cylinder for displacement of the die piston (6) away from the piston (5), and the feed pressure below said pressure opens the connection of the control cylinder to the pressure medium source for displacement of the die piston against the impact piston.