Patent ID: 12251811

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of a linerbolt removal tool100, incorporating a number of improvements compared to conventional linerbolt removal tools as discussed above, will now be described with reference toFIG.1showing the overall configuration and the subsequentFIGS.2A,2B,3A and3Bshowing details of internal elements of the linerbolt removal tool100.

In the following example and the further examples to follow, it will be generally assumed, unless otherwise specified herein, that the construction and functionality of the improved embodiments of the linerbolt removal tool100may be based on embodiments of the conventional linerbolt removal tools as disclosed in the above discussed International Patent Application Publication Nos. WO1997026116 and WO2002081152, the entire contents of which are incorporated herein by reference. However, it should be appreciated that the improvements described herein may also be implemented into other types of linerbolt removal tools that have different construction and/or functionality compared to the above referenced publications, as long as they are compatible with the particular features of the linerbolt removal tool100described herein.

In broad terms, the linerbolt removal tool100includes a housing110; a moil120supported for reciprocating movement along a hammer axis101by the housing110; an inertial body130located within the housing110; a gas charged accumulator140extending from the inertial body130in a rearward direction away from the moil120; a piston160moveable within the inertial body130along the hammer axis101between a striking position at which the piston160strikes the moil120and a retracted position remote from the moil120at which a rear portion of the piston160is retracted within the accumulator140.

As per conventional linerbolt removal tools as discussed above, firing the piston160from its retracted position to its striking position includes causing pressurised gas (such as nitrogen gas) within the accumulator140to accelerate the piston160in a forward direction toward the moil120. In some embodiments, the linerbolt removal tool may have a recoilless action, in which the internal body130may be moveable within the housing110along the hammer axis101, whereby firing the piston160involves causing the pressurised gas within the accumulator140to accelerate the piston160in a forward direction toward the moil120while the inertial body130accelerates in the rearward direction. However, it should be appreciated that this recoilless action is not essential and the improvements described herein may be applied to other types of linerbolt removal tools.

The piston160has a striking end161for striking the moil120and an opposing rear end162. The linerbolt removal tool100also includes a piston cap170that encloses the rear end162of the piston160, wherein during firing the piston160and the piston cap170initially accelerate together and prior to the piston160reaching its striking position the piston cap170separates from the piston160which continues to move in the forward direction until the forward end161of the piston160strikes the moil120, whereby the piston cap170isolates the piston160from the accumulator140.

With reference to the more detailed views of the rear portion of the linerbolt removal tool100inFIGS.2A,2B,3A and3B, a number of improved aspects in relation to the design of the piston cap170will now be described.

In one aspect, embodiments of the linerbolt removal tool100may be configured so that a front portion171of the piston cap170impacts on an impact surface151inside the accumulator140to cause the piston cap170to separate from the piston160(as shown inFIG.2B), and the piston160includes a ledge165that impacts on the front portion171of the piston cap170when the piston160moves in the rearward direction from the striking position towards the retracted position (as shown inFIG.2D), for example during a rebound stroke.

This arrangement enables impact loading to be applied to the front portion171of the piston cap170for both of these scenarios which reduces the overall stress range by allowing the same load conditions for the forward and rebound load cases.

This can be contrasted with conventional piston cap designs, where the piston cap impacts on a front face during the firing stroke and impacts on an inside rear face during a rebound stroke and the stresses induced in the piston cap are very different for these two scenarios. Such conventional piston cap designs are not ideal for these different stress cycles, and as mentioned above, the combination of these opposite stresses cause a higher stress range in the piston cap which leads to cap failure due to fatigue.

However, it will be appreciated that the improved design of the piston cap170addresses this problem in the conventional piston cap designs. Since all impacts now take place at front portion171of the piston cap170(i.e. there are no longer impacts in the rear portion of the cap in dry fire scenarios, etc.), the loads in the rear portion of the piston cap170are significantly reduced. Impact loading at the same end of the piston cap170for forward/reverse scenarios means the piston cap170can be designed with a single stress profile, as opposed to the prior art where the piston cap designs had to account for very different stress profiles due to impacts at either end.

Further operational details of this aspect will now be described.

In the embodiment depicted in the FIGURES, the linerbolt removal tool100includes an impact collar150mounted between the inertial body130and the accumulator140. The piston160slides inside the impact collar150, and in this embodiment the impact surface151is provided on a rear edge of the impact collar150. It will be appreciated that providing the impact surface151on a separate part such as the impact collar150will allow the particular configuration of the impact surface151to be controlled as part of the design of the impact collar150component.

However, it should be appreciated that it is not essential for the impact surface151to be provided on an impact collar150, and in other embodiments the impact surface151may be provided as a suitable surface of another component, such as a surface of the inertial body130facing the accumulator140, a surface inside the accumulator proximate the inertial body130, or a surface of another part generally between the inertial body130and the accumulator140.

FIGS.2A and2Bshow the piston160in a fully retracted position prior to the firing sequence. At the start of the firing sequence the front portion171of the piston cap170is at rest against the ledge165of the piston160. As the firing sequence proceeds the piston160and the piston cap171are accelerated together in the forward direction by the pressurised gas in the accumulator140. Prior to the piston160impacting the moil120the front portion171of the piston cap170impacts on the impact surface151of the impact collar150. The piston160continues travelling forward due to its momentum until it impacts the moil120.

FIGS.3A and3Bshow the piston160separated from the piston cap170due to the front portion171of the piston cap170being in contact with the impact surface151of the impact collar150. As the piston160continues forward the piston cap170isolates the rear end162of the piston160from the gas pressure within the accumulator140, for example via a seal163mounted to the rear of the piston160. An optional hole164through the centre of the piston160is open to atmosphere at the striking end161of the piston and ensures that a volume301created by the separation of the piston160and the piston cap170remains at atmospheric pressure. Further details of this arrangement will be described below.

In some instances where the moil120impacts a highly resilient object the moil120rebounds causing it to impact the piston160and sending it in a rearward direction at velocity. When this occurs the ledge165of the piston160impacts the front portion171of the piston cap170. The gas pressure in the accumulator140acting on the piston cap170brings the piston160and piston cap170to rest.

A number of preferred or optional features of this aspect will now be described.

In some embodiments, the front portion171of the piston cap170may include a single cap impact face for impacting with each of the impact surface151and the ledge165. In this case, the front portion171of the piston cap170may be configured so that an outer region of the cap impact face may impact with the impact surface151and an inner region of the cap impact face impacts with the ledge165. In one example, the cap impact face may have an annular shape with an internal diameter that is less than a diameter of the ledge165and an external diameter that is greater than the diameter of the ledge165.

However, it is not essential to provide a single cap impact face, and in some alternative embodiments, the front portion171of the piston cap170may include a first cap impact face for impacting with the impact surface151and a second cap impact face for impacting with the ledge165. In this case, the first cap impact face may have an annular shape that corresponds to the impact surface151and the second cap impact face may have an annular shape that corresponds to the ledge165. In some implementations, the first cap impact face may be offset rearwardly from the second cap impact face.

In some embodiments, the front portion171of the piston cap170may have a flared profile such that it is thicker proximate to the cap impact face(s), as can be seen inFIGS.2B and3B. This can help to ensure that the front portion171of the piston cap170has adequate strength and stability for withstanding the impact loading.

As shown inFIGS.2B and3B, in some implementations the piston160may include a relief groove inwardly of the ledge165. Additionally or alternatively, in some implementations the impact collar150may be tapered such that its diameter reduces to a minimum diameter at the rear edge of the impact collar150, which in this embodiment provides the impact surface151that impacts with the front portion171of the piston cap170. However, as mentioned above, the use of an impact collar150for providing the impact surface151is not essential and the impact surface151may be provided on another component of the linerbolt removal tool100.

In another aspect, embodiments of the linerbolt removal tool100may be configured so that a rear portion172of the piston cap170has a concavely curved internal cap surface, and the rear end162of the piston160has a convexly curved piston surface166that substantially conforms to the concavely curved internal cap surface.

This arrangement can be contrasted with the conventional piston cap and piston designs which typically have respective internal and external faces having squared ends with radius edges due to these faces impacting each other. High stresses around the internal radius can cause failure of piston caps having this conventional design approach.

It will be appreciated that this aspect addresses this problem by providing the piston cap170with a profile that greatly reduces stress concentrations. In some examples the profile could be in the form of a parabola. Due to the reduction in stress concentrations this also allows for the profile to have a thin wall, greatly helping the total mass of the piston cap170. The mass of the piston cap170is critical to the hammer performance due to the energy wasted to accelerate the piston cap170which does not contribute to the energy imparted by the piston160during use of the linerbolt removal tool100.

A number of preferred or optional features of this other aspect will now be described.

In some examples, the concavely curved internal cap surface may have a substantially parabolic profile, which has been found to be an advantageous profile for optimising the strength of the piston cap170in a rebound stroke scenario.

In some embodiments, the rear portion172of the piston cap has a convexly curved external cap surface, which may also have a substantially parabolic profile. In some implementations, the concavely curved internal cap surface and the convexly curved external cap surface have different curvatures, which may be desirable from a strength perspective.

Preferably, the piston cap170has a thin walled construction, which can enable significant reduction of the mass of the piston cap170, although this is not essential. It should be appreciated that such a thin walled construction of the piston cap170does not necessarily involve a constant wall thickness, and in fact it can be desirable for the thickness of the piston cap170to vary between the front portion171and the rear portion172. As mentioned above, the front portion171of the piston cap170may have a flared profile, i.e. having increasing thickness in the forward direction. In cases where the internal and external cap surfaces of the rear portion172of the piston cap170both have a parabolic curved profile, this can result in increased thickness in the rear section of the cap.

As shown in the FIGURES, the piston cap170will typically include a substantially cylindrical portion extending between the front portion171and the rear portion172. As will be described in further detail below, this will generally facilitate sealing between the piston160and the piston cap170.

In the particular implementation shown in the FIGURES, the rear end162of the piston160also includes a flat rear face167rearwardly of the convexly curved piston surface166, such that a void is defined between the flat rear face167and part of the concavely curved internal cap surface of the rear portion172of the piston cap170.

In one preferred implementation, the piston cap170may be constructed from steel, which can be precision machined to provide a thin walled, light weight component having a specific desired profile for ensuring adequate strength. It is noted that conventional piston caps were typically constructed from nylon for reduce weight, since other design constraints traditionally prevented the thin walled construction that is now available in view of the design improvements to the piston cap170.

In a further aspect, embodiments of the linerbolt removal tool100may be configured so that the piston cap170includes an internal cylindrical surface, and the piston160includes a seal163that sealingly engages with the internal cylindrical surface of the piston cap170such that gas is not permitted to flow between the accumulator140and a volume301that forms between the piston cap170and a rear end162of the piston160when the piston cap170separates from the rear end162of the piston160.

This can be contrasted with prior art arrangements in which the sealing between the piston cap and the piston is achieved using a seal that is provided inside the piston cap so that the seal runs on the outside of the piston. This traditional design approach caused the designed cross section of the piston cap to be bulky, which increases the total piston cap weight and in turn increases stress concentrations within the piston cap. However, this problem can be avoided by relocating the seal163so that it is provided inside the piston160instead, with the seal163running on the internal cylindrical surface of the piston cap170.

Simulations of a piston160impacting a moil120have shown that the stresses are reasonably low proximate to the rear end162of the piston160, and this has allowed the sealing design to change and allowed the seal163to be installed on the outside of the piston160rather than inside the piston cap170. This allows the piston cap170to have a significantly reduced cross section, reducing the overall mass of the piston cap170. This has also allowed for more optimal stress flow into the piston cap170upon impacts.

Typically, the seal163is provided in the piston160proximate to the rear end162of the piston160. In some embodiments, the seal163is embedded in a cylindrical outer surface of the piston160. In preferred implementations, the seal163is a pressure seal embedded in a groove inscribed around a circumference of the piston. As mentioned above, the piston cap170may include a thin walled cylindrical portion (i.e. between the front portion171and the rear portion172), which may provide the internal cylindrical surface along which the seal163runs in use.

In another aspect, embodiments of the linerbolt removal tool100may be configured so that the piston160includes a hole164extending from its striking end161to its rear end162for permitting gas communication between the atmosphere surrounding the striking end161and the volume301between the piston cap170and the rear end of the piston162.

This ensures that the piston cap170always returns to being fully seated on the rear end162of the piston160, without the need for a buffer rod as in prior art linerbolt removal tools. In turn this leads to consistent hammer performance and reduce stress in the piston cap170, noting that the piston cap170will no longer need to be designed to withstand strikes with the buffer rod in a rebound stroke, which has traditionally been a point of failure in conventional piston caps.

It will be understood that this will require sealing between the piston160and the piston cap170. Although this would preferably be achieved using the arrangement described above, wherein the seal163is provided in the piston160, this aspect could also be implemented into any embodiments which include a seal between the piston and the piston cap such that gas is not permitted to flow between the accumulator and a volume that forms between the piston cap and a rear end of the piston when the piston cap separates from the rear end of the piston body, such as in the conventional sealing design seen in the prior art.

Typically, the hole164extends along the hammer axis and is located on a central axis of the piston160. In some examples, the hole164may include a filter mounted in an enlarged opening at the rear end162of the piston160, as shown in the FIGURES.

Although the use of a hole164in this manner is not an essential element of the other aspects described above, it is highly desirable to provide in combination with the other aspects as it will allow the design of the piston cap170to be further optimised by avoiding the need to account for buffer rod loads. If a hole164is not provided, the linerbolt removal tool100may include a buffer rod (not shown) inside the accumulator140for urging the piston cap170onto the rear end162of the piston160when the piston160moves to the retracted position.

It should be understood that the above described aspects of the improvements to the linerbolt removal tool100may be implemented separately or in any combination. Preferred embodiments may combine all of the different aspects, which has been found to allow the design of the piston cap170to be optimised to reduce its likelihood of failure and also reduce its mass which can improve the performance of the linerbolt removal tool by conserving energy that would otherwise be wasted to accelerate the mass of the piston cap170. However, this is not essential, and substantial benefits may be realised by implementing any one or more of these aspects into embodiments of the linerbolt removal tool100.

With reference again toFIG.1and the detailed views of the front portion of the linerbolt removal tool100inFIGS.4A and4B, another improved aspect in relation to the retention of the moil120in the linerbolt removal tool100will now be described.

It should be appreciated that although this aspect may be implemented in embodiments of the linerbolt removal tool100incorporating one or more of the above described improvements in the relation to the design of the piston cap170, this is not essential, and this aspect may be implemented independently without compromising its functionality and associated advantages.

In broad terms, and with regard again toFIG.1, the linerbolt removal tool100in accordance with this aspect includes a housing110; a moil120supported for reciprocating movement along a hammer axis101by a receptacle111in the housing110; an inertial body130located within the housing110; a gas charged accumulator140extending from the inertial body130in a rearward direction away from the moil120; and a piston160moveable within the inertial body130along the hammer axis101between a striking position at which the piston160strikes the moil120and a retracted position remote from the moil120at which a rear portion of the piston160is retracted within the accumulator140. Firing the piston160from its retracted position to its striking position includes causing pressurised gas (such as nitrogen gas) within the accumulator140to accelerate the piston160in a forward direction toward the moil120.

In this aspect, and with regard toFIGS.4A and4B, the linerbolt removal tool100additionally includes cross pins420extending across the receptacle111for limiting movement of the moil120(not shown inFIGS.4A and4B, but shown inFIG.1). When the moil120impacts a linerbolt that is unable to absorb the striking energy imparted to the moil120, forward movement of the moil120is stopped by the cross pins420. The cross pins420are specifically mounted in bushes430,440, which are formed from a resilient material. Preferably, the resilient material is an elastomer. It will be appreciated that, in this arrangement, the cross pins420may be isolated from the housing110using the bushes430,440.

As per conventional linerbolt removal tools which retain the moil120via cross pins, the cross pins420have two purposes, the first being to prevent the moil120from being ejected in the event of a dry fire, and the second being to prevent the moil120from striking the internal elements of the tool in the event of a recoil blow. These scenarios induce high magnitude shock waves through the tool and all critical components, potentially causing failure.

In conventional linerbolt removal tools, the cross pins are horizontally orientated and are normally retained with lynch pins which are susceptible to failure. However, the arrangement shown inFIGS.4A and4Baddresses this issue by isolating the cross pins420from the housing110of the linerbolt removal tool100by introducing elastomer bushes430,440.

A number of preferred or optional features of this aspect will now be described.

In the particular embodiment shown inFIGS.4A and4B, the cross pin bushes430,440are located in the front portion (also referred to as the nose) of the housing110. As shown inFIG.4B, each cross pin420may be mounted in a pair of bushes430,440. In some examples, the two bushes430,440in the pair may have different configurations depending on their location. In this example, each bush430,440may include a flange that engages with a radial recess groove112in the housing110for retaining the bush430,440in the housing110. Thus, the bushes430,440may be held in place using radial recess grooves112. When the cross pins420are installed the bushes430and440are fully locked in position between the cross pins420, the radial recess grooves112and the nose of the housing110.

It is noted that, in this new configuration, the cross pins420are less restrained from movement when impacted, which amplifies the retention issues associated with the current design. However, to overcome this issue, the cross pins420and bushes430,440may be orientated vertically to allow the cross pins420to be held in by gravity (in contrast to conventional cross pins which are oriented horizontally. The cross pins420may be restrained from falling through by a step421at a bottom of each cross pin420, which engages with a corresponding shoulder in a respective lower one of the bushes440, to thereby restrain the cross pin420within the bush440.

As shown inFIG.1, the moil120may include at least one supporting surface123for supporting the moil120within the receptacle111, and at least one engaging surface124for engaging with the cross pins420. The engaging surface124is normally recessed relative to the at least one supporting surface124. Typically, the at least one supporting surface123is substantially cylindrical, and the at least one engaging surface124may be provided in the form of a groove defined around a circumference of the moil120. However, it will be appreciated that the above described arrangement involving mounting the cross pins420in resilient bushes430,440may be implement with other moil120configurations.

As mentioned above, in a dry-fire scenario, the moil120may not actually strike the linerbolt or the linerbolt may be easily removed whilst offering little resistance to the impact. If this occurs, the motion of the moil120within the receptacle111along the hammer axis101will continue unarrested by the linerbolt, until engaging surface124of the moil120engages with the cross pins420. If such a dry-fire scenario occurs during the use of conventional cross pins, extreme shock loading will be encountered as the moil120is suddenly stopped by the cross pins. On the other hand, since the cross pins420are mounted in bushes430formed from resilient material, the shock loading will be partially attenuated by the resilient interface. Accordingly, it will be appreciated that the configuration of the cross pins420and resilient bushes430,440will help to reduce the risk of damage or reduction of operational life in the linerbolt removal tool100due to a dry-fire scenario or similar events.

For the sake of completeness, a number of other practical implementation features of embodiments of the linerbolt removal tool100incorporating one or more of the above discussed aspects will now be described.

The accumulator140may be formed as a substantially blind axial cylinder extending from the inertial body130. The accumulator140may be charged for firing by hydraulically driving the piston160to its retracted position. The accumulator140may be fired by quick release of the hydraulic fluid utilised to drive the piston160to its retracted position. The quick release may be provided by controlling the outflow of the hydraulic fluid utilised to drive the piston160to its retracted position through cascade connected logic elements. The accumulator140may be gas charged external of the housing via a suitably valved charging tube to the inertial body130including a flexible tube section141to accommodate movement of the inertial body130.

The piston160typically slides in a cylinder formed in the inertial body112. The impact collar150may be mounted rearwardly of the cylinder and may be installed together with a sealing arrangement for preventing the escape of gas from the accumulator140into the cylinder during movement of the piston160.

As mentioned above, the inertial body130may be moveable within the housing110along the hammer axis101, whereby firing the piston160from its retracted position to its striking position includes causing pressurised gas within the accumulator140to accelerate the piston160in the forward direction toward the moil120while the inertial body130accelerates in the rearward direction.

The linerbolt removal tool100may include a hydraulic ram assembly180for moving the inertial body130in the forward direction toward the moil120prior to firing the piston160whereby the inertial body130is accelerated in the rearward direction and subsequently decelerated to substantially absorb a reaction generated by firing the piston160. The hydraulic ram assembly180may also be for moving the inertial body130in the rearward direction away from moil120subsequent to firing the piston160.

The hydraulic ram assembly180may include a plurality of fluid inlet ports which are sequentially opened to a working chamber of the hydraulic ram assembly180as the length of the working chamber extends. The hydraulic ram assembly180may be in the form of a double acting ram assembly having a working chamber which converts to a drain chamber upon reverse operation of the hydraulic ram assembly and wherein the plurality of fluid inlet ports become drain ports which are sequentially closed during contraction of the drain chamber.

The inertial body130is typically constrained to move along one or more guides associated with the housing110. In particular, the inertial body130may be supported on linear bearings on a pair of spaced parallel bars which extend parallel to the hammer axis.

As mentioned above, the construction and functionality of the improved embodiments of the linerbolt removal tool100may be based on embodiments of the conventional linerbolt removal tools as disclosed in the above discussed International Patent Application Publication Nos. WO1997026116 and WO2002081152, which disclose further details of other construction features that are not directly associated with the improved aspects of the linerbolt removal tool described herein.

It should be appreciated that the above described linerbolt removal tool improvements may be incorporated with the previously developed examples of linerbolt removal tool, and more than one of the improvements may be incorporated in combination where these are compatible with one another.

It should also be appreciated that the different embodiments of the linerbolt removal tools described herein may be modified to include any one or more of the improvements as described above, in order to enable the described functionalities of the linerbolt removal tool improvements.

Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. As used herein and unless otherwise stated, the term “approximately” means ±20%.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a support” includes a plurality of supports. In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings unless a contrary intention is apparent.

It will of course be realised that whilst the above has been given by way of an illustrative example of this invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is herein set forth.