Patent Publication Number: US-6216895-B1

Title: Lateral jib locking device

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a locking device for telescopic sections of a telescopic jib, and more particularly to the jib of a crane or mobile crane having such a locking device. 
     Crane jib telescopic sections are lockable in the extended condition to, among other things, relieve the load on the telescoping system. This applies especially when use is made of entraining means, for example piston/cylinder units, for extending the telescopic sections in bringing one telescopic section after the other into the extended or retracted positions. 
     For locking telescopic sections use is made mostly of locking pins, which engage from one telescopic section into a receiving portion of the adjoining telescopic section. In earlier practice such pins were retracted from the outer side of a surrounding telescopic section inward into a receiving portion of the telescopic section located within. On the one hand, this is an unsightly disadvantage, since exposed locking units spoil the neat design of the jib as a whole. On the other hand, such conventional jibs and pinning systems necessitate disposing a power supply (hydraulics, pneumatic system, etc) to the pinning means on the outer side of the jib, which is a technical complication to be avoided. 
     In a very early practice, such as disclosed in U.S. Pat. No. 4,036,372 a locking system with locking pins engage from an inner telescopic section outwards into receiving portions of an outer telescopic section, as a result of which the locking system could be disposed in the interior of the jib, thus obviating the need of locating power supplies on the outer side of the jib. However, the drawback in this system is that each of the locking pins engages the upper or lower plates of the telescopic section, i.e. at locations at which maximum bending stresses (tension at the top, compression below) occurs due to the external loads. In addition to this the release device described in this patent operates with double-acting cylinders and is thus, for this reason alone, relatively complicated. 
     Known from EP O 661 213 Al is a locking device for telescopic sections in which a locking pin guided in an inner telescopic section is able to engage a receiving portion in an outer telescopic section. This document describes the use of spring-biased locking pins in which the pin is maintained in a locked position by the force of a spring, whilst the inner end of the pin can be engaged by a hydraulic release device to return the pin into the released position in overcoming the force of a spring. A parallel description of the same design is described in U.S. Pat. No. 5,628,416. 
     In the last-mentioned locking device only a single locking pin is provided for locking two telescopic sections, this locking pin engaging the top flange shells of the jib sections in the middle. Thus, here too, there is again the disadvantage that the passages for the locking pins are provided just in the cross-sectional zone of the jib profile where maximum tensile stresses occur and, therefore, the structure of the jib sections is interrupted at an unsuitable location due to the recesses. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a locking device for telescopic jibs which obviates the above mentioned drawbacks of prior art, it being more particularly the intention to provide a locking device which permits a necessary structural weakening of the jib profile with minimum disadvantage to stability. 
     This object is achieved in accordance with the invention in that two locking pins, each of a locking unit, are arranged on each inner telescopic section so that they can be caused to engage with two oppositely located receiving portions in the vertical side webs of the outer telescopic section, i.e. preferably in the middle portion of the side webs. 
     The special advantage afforded by the locking device in accordance with the invention is that the receiving portions and passages needed for the locking pins are disposed in a zone of the jib in which the bending load forces produce bending stresses in the jib of no significance. In loading a jib or its telescopic sections when lifting a load a maximum tensile stress occurs on the upper side of the profile and a maximum compressive stress materializes on the underside. 
     This also applies to the side webs of the profile, a zone materializing, however, which is substantially stress-neutral in the middle portion of the side web. In accordance with the invention it is just in this substantially stress-neutral zone that the locking units are now disposed so that the structural weakening materializing from the necessary passages in the webs are of minimum disadvantage to the stability in this case. Since the bending stresses occurring in this case are relatively slight, this weakening of the structure is minimal and acceptable. 
     In one preferred embodiment of the present invention the release device comprises a hydraulic actuating cylinder arranged on a piston/cylinder unit, more particularly on the head of the cylinder at the piston output end parallel to the longitudinal axis thereof. The aforementioned piston/cylinder unit serves to extend or retract the telescopic sections and is thus already provided with a hydraulic system. This hydraulic system can be made use of simultaneously to actuate the hydraulic actuating cylinder, which is arranged to advantage space-savingly parallel to the longitudinal axis of the piston/cylinder unit. 
     The release device preferably comprises a lever, which converts the actuation of the hydraulic actuating cylinder so that an engaging end of the lever is moved substantially in the axial direction of the locking pins. By means of such a lever simple and reliable conversion of the direction of movement of the actuating cylinder by 90° is assured. 
     The engaging end of the lever is preferably configured so that on axial travel of the piston/cylinder unit it can be brought into engagement with a clasp at the inner end of the locking pin. For this purpose the engaging end of the lever advantageously comprises a T-shaped protuberance which can be brought into engagement with a longitudinally slotted clasp on the inner end of the locking pin, thus making it possible to bring this release device into the respective position suitable for releasing the locking pins by the method of the release device with the head of the piston/cylinder unit. When the device is moved each time to the suitable location by position monitoring, the engaging end of the lever of the release device engages the inner clasp of the locking pin so that the locked position can be released when the hydraulic cylinder is set in motion. In this arrangement it needs to be assured that the jib sections are retained at all times either by means of the locking pins or are locked in place by an entraining device. 
     In one embodiment of the locking device in accordance with the invention the release device is arranged on the head of the piston/cylinder unit above an entraining device for extending the telescopic sections, the locking pins being located parallel to the entraining pins. In this arrangement the entraining device may be a conventional assembly having extensible entraining pins and receiving portions provided therefor in the telescopic sections 
     In a further advantage aspect of the locking device in accordance with the invention the outer end of the locking pins comprises a nose protruding opposite to the telescopic extension direction. In the locked condition of two sections the nose clasps the adjoining part of the receiving portion behind the outer wall of the outer section. 
     Unlike the fully surrounding safety collars as proposed in prior art (see EP O 661 231 Al) a nose such as above permitting hook attachment to the outer telescopic section thus ensuring that the pin in the locked condition of two telescopic sections cannot be accidentally retracted, has the advantage that when the lock is released, i.e. when the telescopic cylinder is extended somewhat with the inner section to enable the locking pin to be retracted there is no longer the danger of the pin snagging in the direction of telescopic extension or laterally in the receiving portion. 
     Provided on the locking pin furthermore in one advantageous embodiment of the invention is an emergency actuator which, more particularly, engages the inner end at the clasp and which may be an unlocking lever with a screw adjustment. By means of this emergency actuator the locking pin can be returned to a retracted release position should the hydraulic actuator become inoperative. 
     A telescopic jib in accordance with the invention suitable for use, more particularly, on a crane and especially on a mobile crane, comprises a locking device as described above by the various embodiments. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a longitudinal, partial section of a locking and release device in accordance with the invention as viewed from above, whereby only one side of the jib portion is shown; 
     FIG. 2 is a view of a part of the release device as shown in FIG. 1 but on a magnified scale; 
     FIG. 3 is a transverse cross-section through two telescopic sections in the region of the locking device; and 
     FIG. 4 is a detail as shown in FIG. 3 but on a magnified scale. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1 there is illustrated the longitudinal section of a jib portion, namely the left hand portion as shown in FIG. 3 as seen from above, depicting the jib sections  1 ,  2 ,  3  and  4 , which in this sequence make up the crane jib outside in. 
     The locking device will now be discussed on the basis of the locking pin  10  used to lock the two outermost telescopic sections  1  and  2 . The pin  10  is mounted axially shiftable in a housing  11  locked in place in the telescopic section  2 . By its outer end  12  the pin  10  penetrates the outer telescopic section  1  through a receiving portion  5 . To safeguard this locked condition the outer end  12  of the pin  10  features the nose  13  which hooks in place behind the outer wall of the section  1  in the locked condition. 
     As mentioned, the pin  10  is shiftingly mounted in the housing  11 , and it is biased by means of a spring  14  in the direction of the locked position, i.e. outwardly, whereby the spring is supported by an inner ridge on the pin  10  as well as by the inner face end of the housing  11  formed by a welded ring  11   a  serving to guide the pin  10  (see FIG.  4 ), i.e. by its inner end  15 . 
     The inner end  15  of the locking pin  10  penetrates the face end of the housing  11  inwardly, i.e. by a clasp  16  arranged at this location which will be detailed later with respect to FIG.  3 . 
     Also evident from FIG. 1 is a piston/cylinder unit which, on the one hand, is used to retract or extend the telescopic sections by means of an entraining device (not shown) and, on the other, features at the end of the cylinder  30 , where the piston  40  emerges, a head  31  on which a release device  20  to  25  is mounted for the locking pins  10 . 
     This release device consists of a hydraulic actuating cylinder  20  which can be powered via the hydraulic system of the piston/cylinder unit  40 ,  30 . By means of the hydraulic actuating cylinder  20 —when called for by the working sequence and suitable positioning of all elements has been “seen” by the position monitor—the locking pin  10  is released via a system of levers which will now be detailed with respect to FIG.  2 . 
     Referring now to FIG. 2 all parts essential to the release device, except for the hydraulic actuating cylinder  20 , are evident. This release device consists of an adjuster mechanism  21  which can be moved by means of the hydraulic actuating cylinder  20  in the direction as indicated by the upper double arrow B. The left-hand end of the adjuster mechanism  21  engages a lever  22 , which can be pivoted about the pivot axis  23 , which in turn is locked in place by the fastener  25 . 
     The adjuster mechanism  21  is formed by a threaded rod, the effective length of which can be varied. 
     In pivoting the lever  22  the axial movement (relative to the longitudinal axis of the jib) of the adjuster mechanism  21  is converted at the engaging end  24  of the lever  22  into a radial movement as indicated by the double arrow A. The engaging end  24  runs out in a T-shaped protuberance engaging the clasp  16  at the inner end  15  of the locking pin  10 . By means of the radial movement as described, the locking pin  10  can thus be shifted in and out of the housing  11 , i.e. from a released position into a locked position (and vice-versa). 
     Referring now to FIG. 3 illustrating a cross-section in the locking portion, it is now evident that two locking pins  10  in each case by this configuration in accordance with the invention can be caused to engage two oppositely located receiving portions in the vertical side webs of the outer telescopic section. This arrangement is essentially symmetrical so that the following details relate to the left-hand side only. 
     The outer telescopic section  1  is divided on its left-hand side into the upper portion  1   a,  the middle portion  1   b  and the lower portion  1   c.  In a loading situation, for example in lifting a weight by means of the jib, tensile forces become effective in the upper portion  1   a  of the side webs producing the highest tensile stress at the upper end, whereas in the lower portion  1   c  compressive forces are effective with a maximum at the lowermost point. 
     In the middle portion  1   b  of the side webs no, or only minor, material stresses exist, stemming from the bending load. In accordance with the invention the locking device has been placed in this portion so that the necessary material penetrations, for example the receiving portion  5 , weaken the stability of the jib overall only to a negligible extent. 
     It is in this perspective that the locking pin  10  biased in the housing  11  by the spring  14  is in turn to be seen, which passes through the outer telescopic section  1  at the receiving portion  5  by its outer end  12  and the nose  13 . Here, more clearly seen than in FIG. 1, the inner end  15  of the pin  10  is evident, comprising at its innermost position a clasp  16  in which the engaging end  24  of the lever  22  resides, in the condition as shown, the lever  22  being actuated by the release device shown in detail in FIG. 2 via the hydraulic actuating cylinder  20 . Due to the longitudinal slot  16   a  in the clasp  16  the engaging end  24  of the lever  22  is able to enter this clasp  16  in a direction perpendicular to the plane of the drawing in FIG. 3 (i.e. in the axial direction of the jib). 
     When the engaging end  24  is located in the clasp  16 , pivoting the lever  22  (see FIG. 2) enables the engaging end  24  to be moved to the right, as shown in FIG. 3, causing the pin  10  to be likewise moved to the right from the locked position into a released position, as a result of which the spring  14  is compressed, causing the telescopic sections  1  and  2  to be no longer interlocked and they can thus be shifted relative to each other with the aid of an entraining device  60 . 
     The entraining device  60  (generally indicated in FIG. 3) comprises for example the receiving portions  62  provided in the inner telescopic section for the entraining pins  61  located in the head  31  of the piston/cylinder unit  30 , the position of these components again being merely indicated by the broken lines. 
     Also evident from FIG. 3 is a emergency actuator for the locking pin  10 , which in this case simply comprises a lever  50  engaging on one side the clasp  16  and on the other side a fixedly mounted stand. By means of the screw  51  the lever  50  can be pivoted manually to the right, as a result of which the locking pin  10  can be released (manually) even if the hydraulics system has become inoperative. At the same time, the lever prevents rotation of the pin  10  so that the engaging end  24  is always able to travel through the longitudinal slot  16   a  into the clasp  16 . 
     The locking action is sequenced as follows: Once, on extension of the telescopic section  2  by means of the entraining device  60  (i.e. the piston/cylinder unit  40 ,  30 ), the locking pin  10  has attained the position in which it is directly located at the receiving portion  5  in the outer telescopic section, pivoting the lever  22  via the hydraulic actuating cylinder  20  releases the movement of the pin  10  due to the spring bias  14 , and the pin  10  moves outwardly by its outer end  12  into the receiving portion  5  and thus through the outer telescopic section  1 . The inner telescopic section  2  can then be retracted somewhat so that the outer telescopic section  1  hooks into place with the nose  13  of the pin  10 , it thereby being locked in place. The entraining device is then able to release and axially travel the telescopic section  2 . 
     When the lock again needs to be released, the entraining device is travailed axially so that, on the one hand, the entraining pins  61  can be caused to engage the receiving portion  62  and, on the other, the engaging end  24  of the lever  22  of the release device caused to engage the clasp  16  at the inner end  15  of the pin  10 . It is to be noted that at this point all locking pins of the jib in the various telescopic sections are located in the locked condition so that their clasps  16  have the same level radially. To bring this about, the locking pins of the inner telescopic sections are configured shorter as is evident from FIG.  1 . 
     When, then, in the unlocking action, as indicated above, the engaging end  24  is located in the clasp  16  the lever  22  can be in turn pivoted via the hydraulic actuating cylinder  20  so that the engaging end  24  is moved radially to the right (as shown in FIG.  3 ), entraining the pin  10  in its movement and shifting it into the unlocked position with the spring  14  compressed. For this purpose the telescopic section  2  should be extended somewhat by the piston/cylinder unit  40 ,  30  to release the engagement of the nose  13 . 
     In this unlocked position the telescopic section  2  is then retained merely by the entraining pin  61  of the entraining device  60  and can be moved to another position 
     As already mentioned, the individual locking components are each provided in duplicate to the left and right of the longitudinal center plane of the jib, i.e. on both the left and right release devices  20  to  25  and locking pins  10  as well as entraining units  60 - 62  are arranged. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.