NOSE BLOCK ASSEMBLY

Abstract: In a rock-breaking apparatus of the type employing a striker pin and hammer providing shock absorbing means housed within the nose block to protect the nose block and its carrier from primary and/or recoil shock loads during use.

Description: NOSE BLOCK ASSEMBLY TECHNICAL FIELD This invention relates to rock-breaking apparatus of the type employing a striker pin adapted for limited axial movement within a nose block assembly upon impact from a hammer means. This rock-breaking apparatus is described in Australian Patent No. 585274. B ACKGROUND ART This type of apparatus commonly involves large force and shock transmissions from a hammer to a striker pin as a means of breaking rocks. The forces involved in such an action can place high stresses on the entire apparatus including the machinery supporting same. In order to minimise the damage such forces can cause to the apparatus, modifications have been proposed with a view to absorb structurally damaging shock as it occurs in this type of apparatus. Australian Patent No. 585274 discloses rock-breaking apparatus which includes a guide column within which a weight falls under gravity to strike a tool. A piece of shock- absorbing material is located at or near the base of said column such that it enables force to be transmitted from said weight to the tool, while minimising the effect of the impact of said weight on other parts of the apparatus. This arrangement reduces the effect of the impact of the weight on the apparatus. However rock-breaking apparatus of the type disclosed in Australian Patent No. 585274 is often used to break very hard types of rock. Often, this means that several blows will be required to cause a single fracture in the rock. On each occasion where the rock does not break, there occurs a recoil through the tool to the apparatus, causing stress in the entire apparatus and in the carrier for the apparatus. This recoil caused by the inability to fracture a rock is termed in the trade as an " ineffective hit". As can be appreciated the force of a recoil is considerable as there is little resilience in rock and therefore most of the kinetic energy imparted by the falling hammer to the striker pin will be reconverted to impart an upward motion to the striker pin and also to the housing which retains it. 1 SUBSTITUTE SHEET On occasion, there may be what is called a "mishit" this occurs when there is no rock beneath the striker pin. Thus, the kinetic energy imparted from the hammer to the striker pin cannot be further imparted to the rock below. As the motion of the striker pin is halted by the rock-breaking apparatus it must therefore absorb nearly all of the kinetic energy. Again this places considerable stress on the apparatus. Australian Patent Specification AUB27994/77 discloses a shock absorber which operates on the exterior of the guide column of the rock breaker. This external mechanism is large, heavy and expensive as well as requiring considerable maintenance. The extra weight means a larger carrier is required to support the rock breaker adding to the expense of the operation. Mounting the shock absorber externally significantly reduces the strength of the bottom end of the rock breaker. As it is desired to be able to move and manipulate rocks to facilitate breaking them, this reduced strength and increased weight reduces the weight of the rocks capable of being moved by the rock breaker and thus the rate of production. DISCLOSURE OF INVENTION One object of the invention is to address the above problems or to provide the public with a useful choice. According to the present invention there is provided a nose assembly for a rock breaking apparatus of the kind described, said assembly having a retainer supporting a striker pin within a nose block housing, said retainer being located adjacent shock absorbing means of said nose block housing. According to a further aspect of the present invention the housing substantially encloses the retainer and shock absorbing means. It is the inclusion of a retainer for the striking pin adjacent the shock absorbing means which provides the present invention with significant advantages. In contrast to the external mounting present in previous rock breakers, the internal mounting allows the rock crusher to be made smaller have, have less weight and at a lower cost. Further, less expensive carriers can be used. Internal mounting of the recoil shock absorber allows design improvements which give very high strength to the bottom of the rock breaker so that high manipulating forces (that is the ability to shift large rocks) can be applied. Further, greater force can be employed to operate the rock crusher. According to yet a further aspect of the present invention the retainer is sandwiched between the shock absorbing means within the housing. 2 SUBSTITUTE SHEET Some embodiments of the present invention may include a striker pin arrangement for rock breaking apparatus, said arrangement including a striker pin having opposed recesses and striker pin retaining means, said means being adapted to receive said recesses to retain said pin with limited movement relative thereto wherein at the limit of striker pin extension the movement thereof is taken up by said pin retaining means and transmitted to a shock absorbing means. According to yet another aspect of the present invention there is provided a nose assembly for a rock breaking apparatus comprising a housing having inner and outer pin passages, a striker pin chamber accommodating a striker pin and retainer, shock absorbing means positioned within the housing, said striker pin being restrained by said retainer between extended and withdrawn positions and being slidable with respect to said pin passages, an inner end of the striker pin extending into a hammer chamber to which the nose assembly is fixed whilst the other end of the striker pin extends outside the striker pin chamber, the arrangement and construction being such that when the striker pin is struck by a hammer within the hammer chamber and penetrates an object the pin advances from a withdrawn to extended position, and in the event of a mishit, said shock absorbing means absorbs shock loads. According to yet a further aspect of the present invention there is provided a nose assembly for a rock breaking apparatus comprising a housing having inner and outer pin passages, a striker pin chamber accommodating a striker pin and retainer, shock absorbing means positioned within the housing on opposite sides of the retainer, said striker pin being restrained by said retainer between extended and withdrawn positions and being slidable with respect to said pin passages, an inner end of the striker pin extending into a hammer chamber to which the nose block assembly is fixed whilst the other end of the striker pin extends outside the striker pin chamber, the arrangement and construction being such that when the striker pin is struck by a hammer within the hammer chamber and penetrates an object the pin advances from a withdrawn to extended position, and in the event of a mishit or ineffective hit, shock absorbing means on one side of the retainer absorbs shock loads. The striker pin retaining means may further comprise a plate and one or more retaining pins wherein said plate is adapted to locate said retaining pins within a nose block whilst engaging said recesses to retain said striker pin with limited movement relative thereto. It should be appreciated that the terms used in this present specification should be taken in their broadest concept. For example, the term pin should means any device which 3 SUBSTITUTE SHEET can act as a stop, co-operating with the striker pin. For example, the pins may be dowels, flanges or even part of the retainer moulding. The waist may be any appropriate indentation. In some embodiments the retainer may have a waist and the striker pin has appropriate co-operating stops. The shock absorbing means may comprise a number of layers of shock absorbing material of identical, similar or differing resilience. The material from which the shock absorbing means is made can be any appropriate material such as polyurethane or rubber. The use of shock absorbing means to absorb shock loads caused by mishits or ineffective hits greatly reduces the amount of stress which would otherwise be experienced by the rock-breaking apparatus. In some embodiments of the present invention the shock absorbing means may be annular in construction surrounding the striker pin. In one embodiment there may be provided primary shock absorbing means situated near the end of the striker pin that receives the hammer impact. This shock absorbing means can directly interact with the hammer to limit its motion. In preferred embodiments of the present invention there may be provided primary shock absorbing means within the nose assembly housing. In this embodiment, hammer travel is maximised. A further advantage of having the primary shock absorbing means within the housing is that this allows a more compact and sealed nose block assembly. Such an assembly is resistant to the incursion of debris and foreign matter. Not only are the assembly and durability of the nose assembly greatly enhanced, but the fewer number of parts ensures a simpler and cheaper product. There may also be provided secondary shock absorbing means which are of particular use in absorbing the recoil energy transferred back to the striker pin as a result of an ineffective hit (that is a hit which does not fracture a rock) on a rock. Thus the means by which energy can be transferred through to the various shock absorbing means from the striker pin can be achieved by a variety of ways. For example, the striker pin may have a waisted portion which interacts with pins provided in the retainer. The length of the waist may therefore determine the total amount of travel of the striker pin. In the event of a "normal hit" the striker pin initially travels only a portion of the distance allowed by the length of the waist before it hits a rock. The impact of the striker pin fractures the rock allowing the striker pin to travel the maximum distance. Most of the kinetic energy transferred to the striker pin by the hammer has been transferred to the rock causing the fracture to occur and there is little consequent stress on the rock-breaking apparatus. In the event of a "mishit" the striker pin travels the full distance permitted by the waist. As there is no rock to absorb the recoil, the top part of the waist hitting the pins in the retainer transfers downwards the kinetic energy associated with the striker pin to the nose block assembly. It is therefore preferable that there be provided shock absorbing means in close proximity to the retainer which can resist the downward transfer of this energy. In the event of an "ineffective hit" the striker pin bounces off the rock and is restrained by the retainer pressing against the shock absorber means. It is therefore desirable to have shock absorbing means positioned around the retainer holding the pins that can absorb this upward motion. It can be seen that the retainer has a number of purposes which provide advantages of the present invention. The retainer ensures that the striker pin cannot travel more than a certain distance in an upwards or downwards direction. Further, the positioning of the retainer adjacent shock absorbing means allow the shock to be dissipated as a consequence of the shock being transferred from the retainer to the shock absorbing means. BRIEF DESCRIPTION OF THE INVENTION: Aspects of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1: is an end view of a nose assembly for a rock breaking apparatus in accordance with a preferred embodiment of the present invention, and Figure 2: is a sectional view through the nose assembly of Figure 1, and Figure 3: is a further sectional view through the assembly block of Figures 1 and 2, and 5 SUBSTITUTE SHEET Fi ure 4 : is a cross-sectional drawing of a nose assembly for a rock breaking apparatus in accordance with an alternative embodiment of the present invention, and Figure 5: is an end view of a nose assembly for a rock breaking apparatus of Figure 4, and Figures 6. 6a, 7. 7a. 8 and 8a: are diagrammatic drawings illustrating striker pin positions for the apparatus of Figures 1, 2 and 3 during distinct operational situations. BEST MODES FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention illustrated by Figures 1 to 3 is fixed to a hammer column 1 and comprises a box-shaped nose assembly housing generally indicated by arrow 15 having upper and lower pin passages 16 and 17 respectively (which can incorporate plain bearings 18), a striker pin chamber 19 accommodating a striker pin 20, retainer 21, primary shock absorbing means 22 and recoil shock absorbing means 23. The primary shock absorbing means 22 is approximately two to five times the depth of the recoil shock absorbing means 23. Striker pin 20 has two recesses 24 on opposed sides thereof, producing a 'waisted' appearance. The surfaces of the recesses 24 are preferably milled flat, so that they may co-operate with dowels 25 of retainer 21, which has a generally square shape. Apertures 26 are provided for co-operation with dowels 25 for securement of the striker pin 20 in the retainer 16. It can be seen that the arrangement of Figures 1 to 3 provides a balanced manner of holding pin 15 in retainer 21, whilst allowing limited up and down movement. Two sets of aligned apertures 27 and 28 in the nose assembly are provided to facilitate removal and insertion of the dowels 25. A first set of apertures 27 having lesser diameter than the dowels 25 provide access to drive out the dowels 25. A second set of apertures 28 having a larger diameter than the dowels 25 enables the dowels 25 to be inserted in the retainer 21. Apertures 28 can be blocked off with plugs (not shown) and a sealant can be used to block off apertures 27. 6 SUBSTITUTE SHEET The assembly of Figures 1 to 3 is formed by assembling together the elements thereof by fixing bolts (not shown) through apertures 29. Apart from the shock absorbing means, the nose block elements may be made of steel or any other suitable material. The material of shock absorbing means 22, 23 is resilient and is preferably polyurethane or rubber material. The shock absorbing means 22 and 23 can be in one piece as shown or made up from a number of pieces (not shown) of similar or varying resilience. In operation the assembly of Figures 1 to 3 functions as follows: The striker pin 20 is struck by a hammer 2 which transfers the shock through the pin to a subject rock. However, in order to prevent the striker pin 20 from taking up its full extent of axial movement and directly knocking into the nose assembly the direct primary shock absorbing means 22 is located in between the striker pin retainer 21 and the cap plate 30 of the assembly. Upon full uptake of the axial motion of the striker pin 20 the pin retainer 21 comes to rest against the direct primary shock absorbing means 22 thereby absorbing the shock. With respect to Figures 4 and 5, the device comprises a hammer column generally indicated by arrow 1, a hammer 2 and an attached nose assembly generally indicated by arrow 3. The nose assembly 3 includes a closure bush 4, a recessed housing 5, and a primary shock absorbing means 6 which surrounds the inner end of a striker pin 7. The striker pin 7 is supported by a retainer 8 within the recessed portion of the recessed housing 5 and the permissible travel of the striker pin 7 is constrained through pins 9. A second or recoil shock absorbing means 10 is located between the retainer 8 and the inner wall 11 of the recess in housing 5. Retaining pins 12 secure the closure bush 4 with respect to the nose block housing 5. In operation (not shown) and in the event that the rock does not break striker pin 7 carries shock directly up from a rock, which is transferred vertically to retainer 8. Shock is then transferred to recoil shock absorbing means 10. Striker pin 7 has two recesses 13 on opposed sides thereof, producing a 'waisted' appearance. The surfaces of the recesses 13 are preferably milled flat, so that they may co-operate with the pins 9 of striker pin retainer 8 which has a generally square shape. The recess 5 in the housing can be generally square as may be the retainer 8. To 7 SUBSTITUTE SHEET facilitate expansion the recoil shock absorbing means 10 can have a circular outer periphery. The nose assembly 3 is secured to the hammer column 1 by a plurality of tie rods (not shown) which are located in apertures 14 in the hammer column 1 and nose assembly 3. The apparatus of Figures 4 and 5 utilises a direct buffer as an annular shock absorber 6 which directly interacts with the hammer 2 to limit its motion. Location of the primary shock absorbing means 22 within the nose block housing embodiment in Figure 1 to 3 maximises hammer travel. However, the preferred embodiment illustrated in Figures 1 to 3, with the location of the direct buffer offers the advantage of including a more compact and sealed nose block assembly which is resistant to the incursion of debris and foreign matter. The assembly and durability are greatly enhanced while the fewer number of parts ensures a simpler, cheaper product. Figures 6 to 8a illustrate striker pin positions for the nose block of Figures 1 to 3 in different operational modes. In Figures 6 to 8a the pins is shown in "normal hit", "mishit" and "ineffective hit" positions. During a "normal hit" (Figures 6 and 6a) after pin 20 has been struck by hammer 2, and rock R is broken, the pin 20 moves from withdrawn to extended positions. In the event of a "mishit" (Figures 7 and 7a) the impact of the hammer 2 is absorbed by primary shock absorbing means 22. In the event of an "ineffective hit" (Figures 8 and 8a) the pin 20 will recoil which is absorbed by shock absorber means 23 via retainer 21. Thus both in the "mishit" and "ineffective hit" scenarios the affect of large shock loads on the nose block housing are substantially minimised. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims. 8 SUBSTITUTE SHEET

Claims: CLAIMS: 1. A nose assembly for a rock-breaking apparatus having a retainer supporting a striker pin within a nose block housing, said retainer being located adjacent to shock absorbing means of said nose block housing. 2. A nose assembly for a rock-breaking apparatus as claimed in claim 1 comprising a housing having inner and outer pin passages, a striker pin chamber accommodating a striker pin and retainer, shock absorbing means positioned within the housing, said striker pin being restrained by said retainer between extended and withdrawn positions and being slidable with respect to said pin passages, an inner end of the striker pin extending into a hammer chamber to which the nose assembly is fixed whilst the other end of the striker pin extends outside the striker pin chamber, the arrangement and construction being such that when the striker pin is struck by a hammer within the hammer chamber and penetrates an object the pin advances from a withdrawn to extended position, and in the event of a mishit, said shock absorbing means absorbs shock loads. 3. A nose assembly as claimed in claim 1 wherein the housing fully encloses the retainer and shock absorbing means. 4. A nose assembly as claimed in claim 1 wherein in the retainer is sandwiched between the shock absorbing means within the housing. 5. A nose assembly as claimed in claim 1, the arrangement including a striker pin having opposed recesses and striker pin retaining means, the striker pin retainer being adapted to receive said recesses to retain said striker pin with limited movement relative thereto wherein at the limit of striker pin extension further movement thereof is taken up by said retainer and transmitted to said shock absorbing means. 6. A nose assembly for a rock breaking apparatus comprising a housing having inner and outer pin passages, a striker pin chamber accommodating a striker pin and retainer, shock absorbing means positioned within the housing on opposite sides of the retainer, said striker pin being restrained by said retainer between extended and withdrawn positions and being slidable with respect to said pin passages, an inner end of the striker pin extending into a hammer chamber to which the nose block assembly is fixed whilst the other end of the striker pin extends outside the striker pin chamber, the arrangement 9 SUBSTITUTE SHEET and construction being such that when the striker pin is struck by a hammer within the hammer chamber and penetrates an object the pin advances from a withdrawn to extended position, and in the event of a mishit or ineffective hit, shock absorbing means on one side of the retainer absorbs shock loads. 7. A nose assembly as claimed in claim 6 wherein the housing fully encloses the retainer and shock absorbing means. 8. A nose assembly as claimed in claim 7, the arrangement including a striker pin having opposed recesses and striker pin retainer, the striker pin retainer being adapted to receive said recesses to retain said striker pin with limited movement relative thereto wherein at the limit of striker pin extension further movement thereof is taken up by said retainer and transmitted to said shock absorbing means. 9. A nose assembly as claimed in claim 6 wherein the retainer sandwiched between the shock absorbing means within the housing. 10

Applicants: ROCKTEC LTD, ROCKTEC LIMITED
Application year: 1993
Main classification: B25D
IPC codes: B25D17