GB1584810A

GB1584810A - Fluid pressure operated percussion mechanism with remotely operable stroke control

Info

Publication number: GB1584810A
Application number: GB5300877A
Authority: GB
Original assignee: Fried Krupp AG
Current assignee: Fried Krupp AG
Priority date: 1976-12-23
Filing date: 1977-12-20
Publication date: 1981-02-18
Also published as: DE2658455A1; JPS5380304A; SE429515B; SE7714140L; DE2658455C3; FR2375008A1; DE2658455B2; JPS614628B2

Description

(54) FLUID PRESSURE OPERATED PERCUSSION MECHANISM WITH REMOTELY OPERABLE STROKE CONTROL (71) We, FRIED. KRUPP GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, of 103 Altendorfer Strasse, D-4300 Essen 1, Federal Republic of Germany, a German body corporate, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :: This invention relates to a fluid pressure operated percussion mechanism of the type, hereinafter termed the type specified, comprising a cylinder containing a piston which is reciprocable to make repeated impacts on a cooperating stem disposed at one end of the cylinder and à distributor valve which is operated automatically in response to the movements of the piston, and by establishment by the piston of communication between the cylinder and the distributor valve which enables pressure medium to flow between them, to reverse pressure and exhaust connections to the opposite ends of the piston and thereby cause reciprocation of the piston.

With a mechanism of this type, the impact energy imparted to the shank at each impact stroke of the piston is directly proportional to the stroke of the piston and the frequency of impact of the piston on the shank is inversely proportional to the duration of a working cycle which in turn is a function of the time occupied by changeover of the distributor valve at the end of the impact stroke and a.t the end of the return stroke of the piston.

Existing modes of adjustment of a percussion mechanism of the above type are time consuming and cumbersome because for example, a Lafette percussion drill must be moved when adjustment is required from the drilling position to an accessible position and can only be replaced with difficulty. In the case of a crusher including a hydraulic hammer the operating personnel must be continually on the alert, because at the start when the material is being broken into large individual pieces a large piston stroke is returned while later, during crushing to smaller pieces, a smaller impact energy and a corresponding smaller piston stroke are required.

The invention provides a fluid pressure operated percussion mechanism of the type specified, in which the communication between the cylinder and the distributor valve is a single channel which is unmasked by the piston on its return stroke and contains an adjustable throttle, or is afforded by a plurality of channels which are unmarked by the piston in succession on its return stroke and are alternatively selectable by a selector valve to permit pressure medium to pass from the cylinder to the distributor valve, and a selector at a station remote from the cylinder which is operable to adjust said throttle or said selector valve.

The main advantages achieved by the invention is that adjustment of the piston can easily be effected during operation of the mechanism from a remote control point.

In addition to the saving in time, this affords considerable protection to the percussion mechanism.

Embodiments of the invention are illustrated in the accompanying diagrammatic drawings, in which: Fig. 1 shows a percussion mechanism with remote control of the stroke of the piston; Figs. 2a and 2h show other embodiments; Figs 3a and 3b are diagrams showing an embodiment in which the changeover time of the distributor valve may be varied; and Figs. 4a, 4b and 4c are further diagrams illustrating variants of the mechanism shown in Figs. 3a and 3b.

Fig. 1 shows a hydraulically operated percussion mechanism including a piston which is reciprocated in a cylinder 1 to cause its impact face S to impart repeated blows to a shank 11. After each impact, the piston is moved away from the impact plane EE in the direction of the arrow by admission of pressure medium under line pressure to a port 7 and thence through an annular channel 8 to an annular surface 5 on the piston. The cylinder 1 contains grooves 2a - 2d which communicate by individual channels 3a - 3d with a distributor valve 19. When the surface 5 on the piston 6 exposes, for example, the groove 2b, a pulse of line pressure PO supplied through the channel 7, can pass via the annular space 8, the groove 2b, the channel 3b, a groove 4b, a bore 9 and a channel 10 to the valve 19.This responds by changing over an alternative position in which it connects the port 7 to return pressure P,. and applies line pressure P0 to another annular surface at the rear of the piston 6 to cause the resulting differential hydraulic pressure to move the piston in an impact stroke towards the shank 11 to make a further impact in the plane EE. Reversal from the impact to the return stroke is effected by establishment of communication through the chann.el 3b, between the valve 19 and the cylinder, as described later with reference to Fig. 3b, shortly before the impact of the piston, to cause the valve 19 to change over again to apply line pressure P0 to the part 7 and return pressure Pr to the rear end of the piston.

The piston can perform different return strokes SQ. 5 . sod, determined by the position of the piston 12 of a selector valve 13, which determines which of the channels 3a - 3d wil be connected by the grooves 4a 4d to the valve 19 on the return stroke of the piston.

Fig. 1 shows the setting for the stroke st. The channel 3a is blanked off by the piston 12 and it is not until the piston has unmasked the groove 2b that line pressure can flow to the valve 19 and the latter is able to switch the piston over to the impact stroke.

The piston 12 is balanced and is acted on by two opposing forces, namely the pressure of a spring 15 and an opposing control pressure Pr which acts on the surface 16 of the piston. The pressure Pr is applied to the selector 13 through a narrow bore hose 18 from a signal generator 17, constituted by an adjustable pressure regulating valve, which is situated at a remote control station. The control pressures appropriate for the strokes s,. . . 5d of the piston 6 are marked on a scale and can be selected by adjustment of a screw 20.

Figs. 2a and 2b show simple embodiments which provide selection of only two alternative strokes sa and Sb. These include a remotely situated signal generator which consists of a manually operated 2/3 way valve 21 and a selector valve 22 which is a 2/2 way valve. In position I of the valve 21, as shown in Fig. 2a, the line 18 is connected to the tank T. The cylinder 24 has only two grooves 2a and 2b. In the position shown in Fig. 2a the valve 22 has closed the channel 3Q, so that the return stroke of the piston continues until it has unmasked the groove 2b to open a path through the channel 3b for a pulse of pressure to the valve 19. The stroke of the piston is therefore sb.

Shifting of the valve 21 to position II moves the valve 22 to position II, in which the channel 3a is open to the valve 19 and the stroke of the piston is sa.

Fig. 2b is a variant of Fig. 2a. The selector valve 25 is a 2/3 way valve and the operation is analogous to that of Fig.

2a.

Figs. 3a and 3b show another mode of control, in which the cylinder 26 has a single groove 2, through which the pressure pulse may pass to the valve 19 through an adjustable throttle 27 at the end of the return stroke of the piston 6. A determined volume V0 of pressure medium is required to move the valve 19 and this must be supplied by the pressure pulse. The valve itself is indicated symbolically by its mass m < . In position I the pressure pulse has moved mv against the pressure of a spring 28 into the position in which the piston 6 commences its impact stroke towards the shank 11. m requires, in dependence upon the degree of opening of the throttle 27, more or less time to reach position I.

During this time the piston continues to travel in its return stroke a distance depending on its moment of inertia. Adjustment of the throttle 27 is therefore effective to control the energy of each individual impact and the frequency of impact. The delay effect may be considerably increased by connecting an accumulator 29 in parallel with the volume Vv of the valve 19.

The throttle 27 is adjustable by a remote control 17, 18.

As shown in Fig. 3b, during the impact stroke cf the piston 6 the groove 2 is connected by grooves 30 and 31 with the return line Pr. The volume Vv of pressure medium has been displaced in the direction of the arrow as the valve mass mv has been returned to position II by the pressure of the spring 28 and the accumulator 29 has discharged the volume Vsp. The entire volume Vsr + V must pass through the throttle 27 to reach the return line Pr through the grooves 2, 30 and 31. The cross sectional area of the throttle thus also determines the reversal time required by mv to return from position I to II.

Increase and decrease in the reversal time of the valve at each end of the piston stroke correspond respectively to lower and higher frequencies of impact.

The adjustable throttle 27 in Figs. 3a and 3b thus performs two functions. It influ ences, as the result of remotely controlled variations in its cross-sectional area, not only the time required for mv to move from II to I, but also the time required for mv to move from I to II.

The embodiments shown in Figs. 4a and 4b permit of variation of one reversal time only.

Fig. 4a shows control of the time required for the valve 19 to move from the return stroke to the impact stroke, which can be delayed by the throttle 27 remotely controlled through the line 18, while the pressure medium bypasses the throttle via the non-return valve 32 when it flows from the valve 19 to the cylinder. Fig. 4b shows exclusive control of the time required by the valve 19 to move from the impact to the return stroke, the pressure medium bypassing the throttle through the non-return valve 32 when flowing from the cylinder to the valve 19.

Fig. 4c can be regarded as a combination of Figs. 4a and 4b. The two changeover lines are independently variable. When the piston unmasks the groove 2, the pressure medium flows through the throttle 33 and the non-return valve 34 to the valve 19.

The path through the throttle 35 is blocked by the closed-non-return valve 36. When the groove 2 is connected by the groove 30 in the piston 6 with the return line (see Fig. 3b) the pressure medium can flow from the valve 19 and the accumulator 29 through the non-return valve 36 and the throttle 35, the path through the throttle 33 being blocked by the non-return valve 34. The cross sectional areas of the throttles 33 and 35 can be independently varied through the remote control channels 1 8a and 1 8b respectively. The accumulator 29 can be of such size that its influence becomes negligible upon full opening of either one or both throttles.

WHAT WE CLAIM IS: - 1. A fluid pressure operated percussion mechanism of the type specified, in which the communication between the cylinder and the distributor valve is a single channel which is unmasked by the piston on its return stroke and contains an adjustable throttle, or is afforded by a plurality of channels which are unmasked by the piston in succession on its return stroke and are alternatively selectable by a selector valve to permit pressure medium to pass from the cylinder to the distributor valve, and a selector at a station remote from the cylinder which is operable to adjust said throttle or said selector valve.

2. A percussion mechanism according to claim 1, wherein the adjustable throttle controls flow of pressure medium both from the cylinder to the distributor valve and from the distributor valve to the channel.

3. A percussion mechanism according to claim 1, comprising a channel bypassing the throttle and containing a non-return valve which permits flow of pressure medium from the distributor valve to the cylinder.

4. A percussion mechanism according to claim 1, comprising a channel bypassing the throttle and containing a non-return valve which permits flow of pressure medium from the cylinder to the distributor valve.

5. A percussion mechanism according to claim 1, wherein the single channel has two branches, each containing a throttle adjustable from the remote station and a non-return valve, one such valve permitting flow of pressure medium from the cylinder to the distributor valve, and the other permitting flow of pressure medium from the distributor valve to the cylinder.

6. A percussion mechanism according to any of claims 2 to 5, which includes an accumulator connected in parallel with the distributor valve.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ences, as the result of remotely controlled variations in its cross-sectional area, not only the time required for mv to move from II to I, but also the time required for mv to move from I to II. The embodiments shown in Figs. 4a and 4b permit of variation of one reversal time only. Fig. 4a shows control of the time required for the valve 19 to move from the return stroke to the impact stroke, which can be delayed by the throttle 27 remotely controlled through the line 18, while the pressure medium bypasses the throttle via the non-return valve 32 when it flows from the valve 19 to the cylinder. Fig. 4b shows exclusive control of the time required by the valve 19 to move from the impact to the return stroke, the pressure medium bypassing the throttle through the non-return valve 32 when flowing from the cylinder to the valve 19. Fig. 4c can be regarded as a combination of Figs. 4a and 4b. The two changeover lines are independently variable. When the piston unmasks the groove 2, the pressure medium flows through the throttle 33 and the non-return valve 34 to the valve 19. The path through the throttle 35 is blocked by the closed-non-return valve 36. When the groove 2 is connected by the groove 30 in the piston 6 with the return line (see Fig. 3b) the pressure medium can flow from the valve 19 and the accumulator 29 through the non-return valve 36 and the throttle 35, the path through the throttle 33 being blocked by the non-return valve 34. The cross sectional areas of the throttles 33 and 35 can be independently varied through the remote control channels 1 8a and 1 8b respectively. The accumulator 29 can be of such size that its influence becomes negligible upon full opening of either one or both throttles. WHAT WE CLAIM IS: -

1. A fluid pressure operated percussion mechanism of the type specified, in which the communication between the cylinder and the distributor valve is a single channel which is unmasked by the piston on its return stroke and contains an adjustable throttle, or is afforded by a plurality of channels which are unmasked by the piston in succession on its return stroke and are alternatively selectable by a selector valve to permit pressure medium to pass from the cylinder to the distributor valve, and a selector at a station remote from the cylinder which is operable to adjust said throttle or said selector valve.