GB2201364A - Powered hammer - Google Patents

Abstract

A powered hammer comprises a reciprocatable hammer head 12 in the form of a piston movable in a cylinder 14 under the influence of driving fluid. A change-over valve 16 directs fluid to the faces of the piston to drive the head along a hammer stroke or a return stroke. Towards the end of the return stroke, the piston closes a vent 74 to cause pressure to build up within chamber 72. This is communicated along passage 18 to the valve 16, which changes over to initiate the next hammer stroke. <IMAGE>

Description

Powered Hammer The present invention relates to powered hammers and in particular, but not exclusively, to piling hammers.

Piling hammers incorporate a reciprocatable hammer head driven by hydraulic or pneumatic fluid. A valve d.irects the driving fluid as necessary to generate the reciprocation. Various proposals for piling hammers have been made but are considered to be unsatisfactory for various reasons, including that they are not sufficiently reliable. In particular, design of the valve mechanism has presented difficulties, and unsatisfactory operatidn of the valve is a common cause of failure in piling hammers.

It is an object of the present invention to obviate or mitigate these or other disadvantages of the prior art.- The present. invention provides a powered hammer comprising a reciprocatable hammer head in the form of a piston movable in a cylinder under the influence of driving fluid, a change-over valve operable to dir-ect driving fluid to respective faces of the piston to move the hammer head along a hammer stroke or a return stroke, and means operable to cause the valve to change over in response to compression generated-within the cylinder as the hammer head approaches the end-of a stroke.

Preferably the valve change-over means operates during the return stroke to initiate the hammer stroke.

Preferably the change-over valve is a shuttle valve, and the valve change-over means comprise a passage for supplying fluid to move the shuttle, the passage communicating with the cylinder, whereby movement of the piston generates pressure within the passage to cause shuttle movement. Preferably the passage communicates with a chamber defined between the piston and the closed end of the cylinder. Preferably there is provided a vent in the chamber, the vent being open at the start of the return stroke and being closed by the piston as the piston moves towards the end of its return stroke, whereby further movement of the piston along the return stroke generates compression within the chamber.

Preferably the change-over means further comprises a passageway which is opened and closed by movement of the piston and which, when open, may supply driving fluid to the valve to cause the valve to change over.

Preferably driving fluid is supplied to the- chamber during the h-ammer stroke.

Preferably the hammer head is generally cylindrical and has an enlarged head within the cylinder, the head providing an end face upon which driving fluid acts during the hammer stroke, and an annular face upon which driv-ing fluid acts during the return stroke.

Preferably the change-over valve shuttle is movable from a first position in which driving fluid is supplied to the end face of the piston, and a second position in which driving fluid is-supplied to the annular face.

Preferably pressure within the passage is applied to an end face of the shuttle, to cause the valve to change over. Preferably the end face comprises a depression into which the pressure is directed.

Preferably the shuttle is located in a valve housing and comprises two heads connected by a relatively narrow neck, the neck, heads and housing defining a chamber to which driving fluid is supp-lied and from which it may leave through one of the two exit passages according to the-position of the shuttle, the other of the passages in each position being closed by a corresponding one of the heads.

Preferably the valve constantly provides driving fluid to a clamping mechanism operable to retain the hammer in position on a workpiece. Preferably the clamping mechanism is supplied through a passage which communicates with the chamber defined by the neck, heads and housing.

In another aspect of the invention there is provided a powered hammer comprising a reciprocatable hammer head in the form of a piston movable in a cylinder under the influence of driving fluid, a change-over valve operable to direct driving fluid to respective faces of the piston to move the hammer head along a hammer stroke or a return stroke, and a passageway which is opened and closed by movement of the piston and which, when open, may supply driving fluid to the valve-to cause the valveto change over.

Preferably the passageway communicates with the cylinder at a position so chosen that the passageway is opened to receive driving fluid as the piston moves towards the end of its return stroke, whereby the valve is changed over to initiate the hammer stroke.

An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which Referring to Fig. 1 there is shown schematically a powered hammer 10 comprising a reciprocatable hammer head 12 in the form of a piston movable in a cylinder 14 under the influence of-driving fluid. A change-over valve 16 is operable to direct driving fluid to respective faces of the piston 12 to move the hammer head along a hammer stroke or a return stroke Means 18 in the form ofa passage are operable to cause the valve 16 to change over in response to compression generated within the cylinder 14 as the hammer head 12 approaches the end of a stroke (the return stroke).

The components of the powered hammer are shown in Figs. 2 to 6. Referring to Fig. 2, there is shown the housing 20 of the valve 16. The hous-ing 20 comprises a block of steel having a face in which a channel 22 is formed. The channel 22 has a relatively wide section 24 and a relatively narrow section 26 and is of generally semi-circular section perpendicular to its length.

A circumferential groove 28 is cut in the wall of the channel. 22 in its wide section. A second groove 29 is cut partly in the walls of the narrow. section 26 and extends through the. housing 20, away from the channel 22.

The shuttle 30 (Fig. 3) of the valve 16 comprises two heads 32,34 connected by.a neck 36. The heads 32,34 have a width slightly less than the width of the channel sections 24,26, to allow the shuttle to be slidably located in the channel 22, with the large head 34 in the wider section 24, and the. smaller head 32 in the narrow section 26. A layer of lubricant provides a seal between the heads and the housing.

The end face 38 may be planar or may have a circumferential.lip as shown in solid lines, so that the end face forms a depression. The depression may also be deepened into the form of a bore 40 extending into the neck 36, as indicated by broken lines in Fig. 3.

Alternatively, the shuttle may be solid. It is believed that the increased weight thereby achieved may assist in operation of the valve, to be described. The weight may be further increased by enlarging the neck 36 along all or part of its length, although any enlargement must not be such as to prevent the shuttle co-operating with the housing 20 to allow the valve to function in the way to be described.

The body 42 of the hammer is square or rectangular section steel machined to provide a central passageway 48 which forms the cylinder 14. Other passages are machined in the walls of the cylinder 14, for the conveying driving fluid to various parts of the hammer 10.

The valve housing 20 is clamped to the body 42 by means of a clamp plate and four bolts into bolt holes 44.

The housing 20 is installed with the channel 22 facing the body 42 so that the channel 22 is closed by the body 42. When installed, the groove 28 provides communication between the channel 22 and a passage 46 which extends through the wall of the body 42, to the cylinder 14. The groove 29 provides communication between the channel 22 and the mouth of a bore 50 which runs in the cylinder wall up to the closed end 52 of the cylinder 14. The bore 50 enters the cylinder close to the closed end 52. The bore 50 may branch as shown to provide two routes from the valve housing to the cylinder 14. Alternatively, one or other route could be used alone. In practice, ease of manufacture and the strength of the resulting structure are likely to be the criteria governing the route of the bore 50.

The cylinder-14 houses the-hammer head 12 shown in Fig. 5. The head is-an elongate'circular cylinder having a narrow portion 54 and a wide portion 56 meeting at a shoulder 58. The narrow portion -54 finishes in a bit 60 which will make impact on workpieces when the hammer is in use. The bit has rounded edges to reduce damage to the hammer head or workpieces. The wide section 56 includes grooves for carrying sealing rings, and may also have further grooves for the retention of lubricant. A further lubricant reservoir may be provided, if desired, by forming a depression in the end face of the wide portion.

A depression of this type is not shown in the drawings.

The end face of the wide portion also preferably has rounded edges to prevent the edges damaging the walls of the cylinder as the hammer head moves.

The narrow portion 54 is of sufficient diameter to be a close. sliding fit in the cylinder 14 near the open end of the cylinder.

Sealing rings carried by the wide end 56 provide a seal between the wide end and the wails of the cylinder 14, nearer the closed end of the cylinder. The hammer head 12 therefore divides the cylinder 14 into two chambers. One chamber is formed between- the shoulder 58, the corresponding shoulder 62 in the walls of the cylinder 14, the outer surface of the narrow portion 54 and the cylinder walls. A second chamber is defined between the end face 64 of the wide e.nd 56 of the head 12, and the cylinder walls, because the axial length of the wide end 56 is considerably less than the axial length of the cylinder 14 between the shoulder 62 and the closed end of the cylinder 14.

The structure and operation of the valve 16 can be described with reference to Fig. 6 which is a partially schematic view showing the shuttle 30 in position in the valve housing 20. In the shuttle position shown, the chamber formed around the neck 36 is supplied with pressurised driving fluid through a supply port 66. This is- in communication around the neck 36 with the exit port formed by the groove 28 so that the driving fluid may enter- the passage 46 and the chamber between. the shoulders 58,62-. The hammer head 12 will therefore be driven towards the closed end of the cylinder 14, so retracting the bit 60. This constitutes the return -stroke of the head 12.

In the other shuttle position indicated with broken lines in Fig. 6, the head 34 closes the groove 28 from the chamber around the neck 36. The head 32 moves off the groove 29, so that driving fluid passes into the groove 29 and vents through the bore 50 to the chamber formed in the closed end of the cylinder 14.

It will be appreciated that in both shuttle positions, pressurised fluid may leave-the valve housing 20 through an exit port 68 which is used to convey driving fluid 'to a mechanism for clamping the hammer to the workpiece. This provides improved performance, especially when the hammer is used for piling.

The sequence of operation of the hammer described above can be understood from the schematic diagrams, Figs. 1,7, and 8. It can be seen that, in each case, there are two chambers within the cylinder 14, namely a chamber 70 between the shoulders 58,62 and a chamber 72 at the closed end of the cylinder. 14. The passage 46 communicates with the chamber 70. The bore 50communicates with the chamber-72. A.further passage 18 communicates with the chamber 72. Finally, a vent 74 is provided for the chamber 72. Pressurised driving fluid provided along the line 76 is directed by the valve 16 to the passage 46 or 50 according to whether the head 12 is in its return stroke or its hammer stroke.

In Fig. 1, the head 12 is embarking on its return stroke. Driving fluid is being supplied to.the chamber 70 to withdraw the head 12. The vent 74. is clear, so that the chamber 72 is vented toa.tmosphere. As the head 12 continues to. withdraw, the position shown in Fig. 7 is reached, in which the head 12 has moved over the vent 74, so closing the chamber 72. As the head 12 continues to withdraw, compression is generated within the chamber 72.

Since the bore 50 is closed by the valve 16, this compression is transmitted along the passage 18 to the valve housing 20, which it enters. to bear on the end face of the head-34 of the shuttle 30. Eventually, this pressure overcomes the pressure of the drive fluid supply around the neck 36, so that the shuttle is moved to its alternative position shown inFig. 8 and in broken lines in Fig. 6..In this alternative posi.tion., drive fluid is suppl.ied.to the chamber 72 so that the. head 12 is driven on its next hammer stroke. When the head approaches the end of its hammer stroke, the. vent 74 opens again.

Accordingly, pressure causes to be.applied to the end face of the shuttle through the passage 18, and the shuttle moves back to the position shown in Fig. 6 under the influence of the supply pressure, thereby initiating the next return stroke. Throughout this cycle, the port 68 has been supplying driving fluid tn the clamping mechanism shown schematically in Figs. 1,7 and 8., Many variations and modifications of the embodiment described.above may be made without departing from the scope of the present invention. For instance, many different physical embodiments of the underlying circuit for the driving fluid can be devised.

One variation incorporat.es an additional passage extending from the. cylinder 14 at. a position between the vent 74 and the point at which the passage 46 enters the cylinder 14. The additional passage communicates with the passage 18. Its position is chosen so that the wide portion 56 opens it into the. chamber 70 shortly before the hammer head reaches the end of its return stroke.

Supply pressure is then s.upplied from the chamber 70 to the valve 16 to provide a positi..ve change over of the valve, and into the chamber -72' to .initi'ate the return stroke.

It may be advantageous. to provide a vent to atmosphere from the chamber formed in part by the end face of the head 32, so that movement of the shuttle to the position shown in Fig. 6 is not hindered by the formation of a vacuum in that chamber. This vent is preferably located to avoid operators of the hammer being sprayed by oil mist which may be ejected during use of the hammer.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims (18)

1. A powered hammer comprising a reciprocatable hammer head in the form of a piston movable in a cylinder under the influence of driving fluid, a change-over valve operable to direct driving fluid to respective faces of the piston to move the hammer head along a hammer stroke or a return stroke, and means operable to cause the valve to change over in response to compression generated within the cylinder as the hammer head approaches the end of a stroke.

2. A hammer according to claim 1, wherein the valve change-over means operates during the return stroke to initiate the hammer stroke.

3. A hammer according to claim 1 or 2, wherein the change-over valve is a shuttle valve, and the valve change-over means comprise a passage for supplying fluid to move the shuttle, the passage communicating with the cylinder, whereby movement of the piston generates pressure within the passage to cause shuttle movement.

4. A hammer according to claim 3, wherein the passage communicates with a chamber defined between the piston and the closed end of the cylinder.

5. A hammer according to claim 4, wherein there is provided a vent in the chamber, the vent being open St: the start of the return stroke and being closed by the piston as the piston moves towards the end of its return stroke, whereby further movement of the piston along the return stroke generates compression within the chamber.

6. A hammer according to any of claims 3 to 5, wherein the change-over means further comprises a passageway which is opened and closed by movement of the piston and which, when open, may supply driving fluid to the valve to cause the valve to change-over.

7. A hammer according to any of claims 3 to 6, wherein driving fluid is supplied to the chamber during the hammer stroke.

8. A hammer according to any of claims 3 to 7, wherein the change-over valve shuttle is movable from a first position in which driving fluid is supplied to the end face of the piston, and a second position in which driving fluid is supplied to the annular face.

9. A hammer according to any of claims 3 to 8, wherein pressure within the passage is applied to an end face of the shuttle, to cause the valve to change-over.

10. A hammer according to claim 9, wherein the end face comprises a depression into which the pressure is directed.

11. A hammer according to any of claims 3 to 10, wherein the shuttle is located in a valve housing and comprises two heads connected by a relatively narrow neck, the neck, heads and housing defining a chamber to which driving fluid is supplied and from which it may leave through-one of the two exit passages according to the position of the shuttle, the other of the passages in each position being closed by a corresponding one of the heads.

12. A hammer according to any of the preceding claims, wherein the hammer head is generally cylindrical and has an enlarged head within the cylinder, the head providing an end face upon which driving fluid acts during the hammer stroke, and an annular face upon which driving fluid acts during the return stroke.

13. A hammer according to any of the preceding claims, wherein the valve constantly provides driving fluid to a clamping mechanism operable to retain the hammer in position on a workpiece.

14. A hammer according to claim 13, wherein the clamping mechanism is supplied through a passage which communicates with the chamber defined by the neck, heads and housing.

15. A powered hammer comprising a reciprocatable hammer head in the form of a piston movable in a cylinder under the influence of driving fluid, a change-over valve operable to direct driving fluid to respective faces of the piston to move the hammer head along a hammer stroke or å return stroke, and a passageway which is opened and closed by movement of the piston and which, when open, may supply driving fluid to the valve to cause the valve to change-over.

16. Ahammer according to claim 15, wherein the passageway communicates with the cylinder at a position so chosen that the passageway is opened to receive driving fluid as the piston moves towards the end of its return stroke, whereby the valve is changed over to initiate the hammer stroke.

17. A hammer substantially as described above with reference to the accompanying drawings.

18. Any novel subject matter or combination including novel subjec-t matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.