WO2007054675A1

WO2007054675A1 - Impact machine

Info

Publication number: WO2007054675A1
Application number: PCT/GB2006/004141
Authority: WO
Inventors: Peter Jeffrey
Original assignee: International Engineering Components Limited
Priority date: 2005-11-11
Filing date: 2006-11-06
Publication date: 2007-05-18
Also published as: WO2007054674A1; GB0523008D0

Abstract

A striking body (16), which is often called a “tup”, is mounted in a housing (10) so as to be capable of reciprocation therein to transmit successive impacts to a tool, such as a chisel (20) or a hammer, optionally by way of an anvil (18). A cam form (14, 24) rotated by a motor (12) or other drive mechanism serves repeatedly to displace the striking body (16) in a direction away from the tool (20) against bias of elastic means (30). Each time, upon release of the striking body (16) from active cam displacement, its striking blow is powered by release of energy from the elastic means (20) along with acceleration of the striking body itself.

Description

IMPACT MACHINE

Machines for breaking rock, concrete and other construction materials are widely used and fall into two principle types, namely hand-held machines and machine-carried machines.

Such machines typically work on the principle of a heavy weight (known as "a tup") being propelled back and forth by a driving force with the forward limit of travel being the impact of the tup onto a chisel (directly or via an anvil) to transfer impact energy onto the material to be broken up. The reverse travel of the tup only repositions the tup for the next impact stroke.

The majority of breaking machines utilise compressed air or hydraulic power to propel the tup back and forth and the energy spent on the reverse stroke is simply wasted. Worse, the recoil generated as the tup reaches the end of its stroke is transferred to the person or the machine carrying the breaking machine. In the case of hand-held machines this necessitates a very heavy machine in order to reduce the damage done to the operative by the recoil transferred to the operative.

A further disadvantage of current designs of breaker is that, where the breaker is powered by compressed air, the escape of the air at the end of each stroke creates a very significant noise, so much so that most road breakers used now have to have silencers fitted which dramatically reduce their efficiency.

None of the current designs allow for the internal mechanism of the machine to be isolated from the dust produced by the breaking action. This dust acts like grinding paste and rapidly wears the mechanism.

Further, most current designs are not capable of incorporating a facility to prevent the striking action of the tup when the chisel is not in firm contact with the material to be broken. Such actions are referred to as "dry strikes" and they result not only in wasted energy but, more importantly, in tremendous shock being transferred to the person or the machine carrying the breaker.

Machines for driving posts into the ground and machines for driving piles into the ground are also well known and operate on similar principles to those outlined above, except that the rock breaking chisel is replaced by a hammer. Such machines are rarely hand held. They are typically mounted onto vehicles, such as tractors or trucks in the case of post drivers and larger excavation machines in the case of pile drivers.

The object of the invention is to limit the energy required to propel the tup to that for only one of its directions of travel so as to increase efficiency, reduce weight, reduce recoil and increase impact/breaking energy.

US 1 ,768,718 (Soderberg) discloses an impact machine wherein a striking body is mounted in a housing so as to be capable of reciprocation therein to transmit successive impacts to a tool, such as a chisel or a hammer. It has a displacement mechanism operative to displace the striking body in a direction away from the chisel or hammer against bias of elastic means so that, upon release of the striking body from the displacement mechanism, its striking blow is powered by release of energy from the elastic means along with acceleration of the striking body itself. In US 1,768,718 the striking body is of magnetic material and the displacement mechanism takes the form of a solenoid which surrounds a non-magnetisable casing in which the striking body is mounted.

The present invention provides an effective alternative impact machine in which the mechanism for displacement of the striking body is a drive mechanism which includes a rotatable cam form. This serves to displace the striking body (hereinafter referred to as a "tup") only in a direction away from the chisel or hammer.

Because the tup is pulled back against elastic means and is then released so that it travels forwards under the stored power of the elastic means, the energy demand is reduced, the impact/breaking power is increased, the recoil is reduced, the machine can be lighter and the machine can be quieter than other currently available impact machines which are hand held or are relatively light weight, but vehicle mounted machines.

The present invention will be described further, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-section of a first embodiment of a machine of the invention in the form of a hand-held road breaker, often known as a "Jack-hammer"; Fig. 2 is a plan view of the cam form of the machine shown in Fig. 1 ;

Fig. 3 is a side view of the cam form of the machine shown in Fig. 1;

Fig. 4 is a linear diagram of the form of the cam on the cam form of Figs. 2 and 3;

Fig. 5 is a side view of the tup of the machine shown in Fig. 1 ;

Fig. 6 is also a side view of the tup of the machine shown in Fig. 1 , but turned through 90° compared to Fig. 5;

Fig. 7 is an underside view of the tup of Figs. 5 and 6;

Fig. 8 is a schematic longitudinal cross section of part of a second embodiment of a machine of the invention in the form of a heavier duty vehicle-mounted breaker or pile driver, the machine frame not being shown here for reasons of clarity;

Fig. 9 is a cross-section along line A-A of the cam mechanism shown in Fig. 8 and the surrounding machine frame; and

Figs. 10 and 11 are schematic fragmentary cross-sections illustrating a dry strike elimination mechanism in a machine in accordance with the invention.

Figs. 1 to 7 show a practical embodiment of a relatively light weight version of an impact machine in accordance with the invention in the form of a hand-held breaker, such as a Jack-hammer. It comprises a generally cylindrical housing 10 inside which are mounted a motor 12, a cam form 14, a striking body, hereinafter referred to as a "tup", 16 and an anvil 18, in that order, as shown in Fig. 1. A robust helical spring 30 is mounted between the tup 16 and a cam form casing 13, in which the motor 12 and the cam form 14 are mounted.

The motor 12 may be powered by compressed-air, electricity, hydraulic power, internal combustion or any other means. In use it drives the cam form 14 through suitable gearing within the casing 13. The axis of the motor 12 and of the cam form 14 is the same as that of a chisel 20 which is mounted to extend from adjacent the anvil 18 out of a cylindrical bush 11 at the end of the housing 10.

The anvil 18 is held in place by a heavy-duty flexible diaphragm 32 eg. of textile reinforced rubber.

A handle 15 is provided at the other end of the housing 10, above the motor 12.

The cam form 14 has a cylindrical surface which is provided with a cam 24, the shape of which is clearly depicted in Figs. 3 and 4. It has two curved rises 22 to respective peaks 23, and then substantially rectilinear (vertical) falls 25, to troughs 26 which lead back into the next rise 22. The two halves of the cam path match each other so that they act simultaneously and to the same extent upon respective cam followers in the form of roller bearings 28 attached to upwardly extending arms 29 of the tup 16. By way of these bearings 28 and arms 29 the cam 24 serves pull the tup 16 upwards against the force of the spring 30 which, as mentioned, is located between the tup 16 and the cam form casing 13.

When the cam followers 28 reach the peaks 23 of the cam 24 they are released and the force of the spring 30 drives the tup 16 onto the anvil 18. The anvil 18 transfers the force onto the chisel 20 to break material against which it is placed. After each percussion/power stroke of the tup 16, the cam-followers 28 are picked up by the cam 24 and the tup 16 is again raised, compressing the spring 30, ready for the next power stroke.

The tup 16 in its lower region is provided with four equally spaced longitudinal grooves 36, as shown in Fig. 7, which fit slidingly onto corresponding longitudinal guide rails 34 inside the housing 10. In this way the tup 16 is constrained to reciprocate in alignment within the housing 10, i.e. vertically up and down, as shown in Fig. 1.

A load detector arrangement is built into the anvil assembly to prevent the drive means from operating unless the chisel 20 is in firm contact with the material to be broken. When firm contact is made, by a load applied to the breaker, via the handle 15, by an operative, the chisel 20 is moved back slightly against the resilient effect of the diaphragm 32. This movement causes a switch mechanism or a valve mechanism in the energy feed to the motor 12 to be opened (or closed) so as to allow the motor 12 to operate. In Fig. 1 a switch 38 is shown, which is part of such a load detector arrangement. This switch 38 is actuated when there is no load applied to the chisel 20 and it is hanging down under gravity with the diaphragm 32 deformed slightly downwards. Actuation of the switch 38 cuts out power to the motor 12.

Such a machine in accordance with the invention is very much lighter than a conventional Jack-hammer. A conventional machine typically weighs over 25kg whereas a comparable machine in accordance with the invention would weigh less than 15kg. Additionally, a machine in accordance with the invention has a much more powerful breaking stroke than a conventional machine. A conventional machine typically has a breaking stroke of 70 to 90 Joules whereas a machine in accordance with the invention could have a breaking stroke of over 200 Joules. Although the machine of the invention operates at a lower frequency (less strokes per minute) it actually breaks materials at a rate at least double that of a conventional breaker. Moreover, the machine in accordance with the invention has almost no recoil and uses less than half of the energy demanded by a conventional machine. Also, the machine of the invention preferably incorporates the above-mentioned dry-strike prevention mechanism and is very much quieter than conventional machines as there is no shock exhaust as with conventional road breakers.

Where a breaker is to be carried by a small to medium excavating machine the size and power of the elastic means/spring utilised in the system must be much more than in hand-held versions. Therefore the cam mechanism must be more robust so as to have a cost-effective life under much greater loads. Having the cam form rotating on the same axis as the chisel is therefore not ideal as the space available for the cam followers (which must carry the loads) is limited. Therefore for this larger machine a cam system has been devised which is mounted at 90 degrees to the chisel axis across the top of the tup. This cam system is illustrated in Figs. 8 and 9. It works in a comparable manner to that described above with all of the same advantages.

With reference to Figs. 8 and 9, in an embodiment of the invention having this style of cam mechanism, a tup 66 is again mounted in a machine housing or frame 60 for reciprocation therein. However, in place of the arms of the above described embodiment, the tup 66 is mounted between lower sections of a pair of opposed plates 69 and a roller 68 mounted between upper margins of these plates 69 serves as a cam follower. The plates 69 are guided within slots 61 in the frame 60 so that the tup is constrained to reciprocate in appropriate vertical alignment within the frame. Cross walls 62 of the frame 60, which define the aforesaid slots 61 , also serve to mount a cam axle

63 upon which a cam 64 is mounted. The cam axle 63 is arranged substantially at 90° to the vertical axis of the frame 60 and the direction of travel of the tup 66.

The anvil and the chisel or hammer of this embodiment are not shown in the drawings, but would be located below the tup 66 in Fig 8.

A helical spring 70 is located between the tup 66 and abutment flanges 71 on the machine frame 60.

The cam 64 is driven by a motor (not shown) by way of a worm gear 65 engaging a central gear 75, as shown in Fig. 9.

The cam 64 is of progressively increasing radial extent with a radial drop 67 between the largest and shortest locations on the circumference. Thus, as the cam 64 is driven in the direction shown in Fig 8, the cam follower 68 and the tup 66 attached thereto are raised. Once the cam follower 68 reaches the point shown in Fig. 8, it falls over the radial drop 67 and the force of the compressed spring 70 assists the fall of the tup 66 in a striking blow onto the anvil below. The distance moved by the tup 66 is less than the distance of the drop 67 and as the cam 64 rotates it again engages and raises the cam follower 68 and thereby raises the tup 66.

Figs. 10 and 11 illustrate a modified form of dry strike elimination means which could be used in place of that depicted in Fig. 1 , but also in respect of any embodiment of the invention. For ease of reference, the same numerals are used to denote comparable parts to those in Fig. 1 and these will not be described again.

A micro-switch 39 is attached to the anvil 18. When the chisel 20 is in contact with firm material M, as shown in Fig 10, its upper end contacts the anvil 18 and pushes it upwards slightly to lift the tup 16 off rubber support blocks 17 in the housing 10. This is possible because the anvil 18 is mounted by means of the resilient diaphragm 32, as described before. In this position the switch 39 contacts a flange 33 within the housing 10 and is switched "on", thus allowing the motor circuit to operate to drive the cam form so that the machine as a whole will operate. In contrast, as shown in Fig. 11, when the chisel 20 is not firmly pressed onto the material M, no load is applied to the anvil 18 and the tup 16 and the latter rests on the blocks 17, at which position the micro-switch 39 is not switched on by contact with the flange 33 so the motor (not shown here) does not operate.

In other embodiments the micro-switch could be mounted on the tup instead of on the anvil. It could also be replaced by a mechanical arrangement, such as a rod acting on a physical valve at the top of the housing, e.g. when the motor is powered by compressed air.

The foregoing is illustrative not limitative of the scope of the invention and many variations in details of the design of the machine are possible and will be apparent to those skilled in the art. In particular, the spring means or elastic means described above could be replaced by any other suitable spring or elastic means, including sealed cylinder means. In all embodiments the mechanism, except for the projecting chisel or hammer or the like, is preferably enclosed within a sealed housing to exclude dust caused by the breaking action. Automatic lubrication within the housing, e.g. by oil mister, is also advantageous.

Claims

1. An impact machine comprising a striking body which is mounted in a housing so as to be capable of reciprocation therein to transmit successive impacts to a tool, such as a chisel or a hammer, a displacement mechanism operative to displace the striking body only in a direction away from the tool against bias of elastic means so that, upon release of the striking body from the displacement mechanism, its striking blow is powered by release of energy from the elastic means along with acceleration of the striking body itself, characterised in that the displacement mechanism is a drive mechanism which includes a rotatable cam form.

2. An impact machine according to claim 1 wherein the elastic means comprises a compression spring or an elastic rope.

3. An impact machine according to claim 1 or 2 wherein the cam form is rotatable on an axis which is aligned with the axis of the tool.

4. An impact machine according to claim 1 or 2 wherein the cam form is rotatable on an axis which is arranged substantially perpendicular to the axis of the tool.

5. An impact machine according to any preceding claim further including an anvil mounted in the housing by way of a resilient diaphragm at a location between the striking body and the tool so as to transmit impact energy from the striking blow of the striking body to the tool.

6. An impact machine according to claim 5 further including dry strike elimination means to prevent the cam form from operating when there is insufficient load applied on the tool to move the anvil back by a pre-determined distance.

7. An impact machine substantially as hereinbefore described with reference to and as illustrated by Figs. 1 to 7 or Figs 8 and 9 of the accompanying drawings.