WO2009089628A1

WO2009089628A1 - Upper hoist limiter

Info

Publication number: WO2009089628A1
Application number: PCT/CA2009/000048
Authority: WO
Inventors: Eric Beaulieu
Original assignee: Load Systems International Inc.
Priority date: 2008-01-16
Filing date: 2009-01-16
Publication date: 2009-07-23
Also published as: WO2009089628A8

Abstract

Described herein is an upper hoist limiter including a relatively heavy body that is suspended to the upper portion of a crane by a chain. A hoist cable of the crane is encircled by the body but is free to slide therein. When the hook block lifts the body, the tension on the chain is removed and the state of a switch enclosed in the body changes. A signal indicating this change of state is supplied to the crane operator so as to stop the upward movement of the hook block.

Description

TITLE

Upper Hoist Limiter

FIELD

[0001] The present invention generally relates to cranes and other hoisting apparatuses. More specifically, the present invention is concerned with an upper hoist limiter for cranes or other hoisting apparatuses.

BACKGROUND

[0002] Cranes and other hoisting apparatus generally use an upper hoist limiter to prevent the hook block from being hoisted beyond the maximum safe height and collide into the upper sheave block.

[0003] The most common method to achieve this is to use a weight wrapped around the hoist line and suspended by chain connected to a switch. Such a conventional arrangement is illustrated in Figure 1 , which is labelled "Prior Art".

[0004] When the hook block is hoisted to the suspended position of the weight, it picks up the weight. This removes the tension in the chain. The chain is connected to a switch either spring loaded or pulled by gravity using a counterweight mechanism. Without the tension in the chain, the sensor arm lifts and cuts (or makes) an electrical contact. The electrical contact is then conveyed to the operator cab or the controls to warn the operator and/or stop the apparatus motion.

[0005] The conventional arrangement illustrated in Figure 1 has many drawbacks. For example, it uses many separate parts that are prone to breakage. Furthermore, the installation of the switch at the end of the crane requires the switch to pivot for adequate operation at any crane angle. This pivot installation requires maintenance. Also, the weight (and thus length) of the chain of the conventional arrangement must be taken into account when the arrangement is set-up.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In the appended drawings:

[0007] Figure 1 , which is labeled "prior art", is a side elevation view of a conventional upper hoist limiter;

[0008] Figure 2 is a isometric view of an upper hoist limiter according to an illustrative embodiment;

[0009] Figure 3 is a isometric view of the body of the upper hoist limiter of Figure 2;

[0010] Figure 4 is a isometric view of the empty body of the upper hoist limiter of Figure 2;

[0011] Figure 5 is a isometric view of the body of the upper hoist limiter, the access covers being removed therefrom;

[0012] Figure 6 is a front elevation view of the upper hoist limiter of

Figure 2;

[0013] Figure 7 is a sectional view taken along line 7-7 of Figure 6; [0014] Figure 8 is a isometric view of an upper hoist limiter according to a second illustrative embodiment; and

[0015] Figure 9 is an isometric view of an upper hoist limiter according to a third illustrative embodiment.

DETAILED DESCRIPTION

[0016] In accordance with an illustrative embodiment, there is provided an upper hoist limiter to be mounted between the boom of a crane and a hoist cable, the hoist cable supporting a hook block, the upper hoist limiter including: a bracket so configured as to be mounted to the boom; a chain having a first end mounted to the bracket and a second end; a body mounted to the second end of the chain; the body being so configured as to encircle the hoist cable so as to allow the hoist cable to slide therein; the body including:

- a rod to which the second end of the chain is attached; the rod being slidably inserted in the body via an aperture;

- a switch so interposed between the body and the rod that a) when the weight of the body is supported by the chain, the switch is in a first state and b) when the weight of the body is lifted by the hook block, the switch is placed in a second state by the relative movement between the body and the rod; wherein the state of the switch is supplied to an operator of the crane. [0017] In accordance with another illustrative embodiment, there is provided an upper hoist limiter to be mounted between the boom of a crane and a hoist cable, the hoist cable supporting a hook block, the upper hoist limiter being mounted to the boom via a chain having a first end mounted to the boom and a second end, the upper hoist limiter including: a body configured as to encircle the hoist cable so as to allow the hoist cable to slide therein; the body including:

- a rod to which the second end of the chain is attached; the rod being so inserted in the body via an aperture as to reciprocately move between an extended position and a retracted position;

- a switch so interposed between the body and the rod that a) when the weight of the body is supported by the chain, the rod is in the extended position and the switch is in a first state and b) when the weight of the body is lifted by the hook block, the rod is moved to the retracted position and the switch is placed in a second state; wherein the state of the switch is supplied to an operator of the crane.

[0018] The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one", but it is also consistent with the meaning of "one or more", "at least one", and "one or more than one". Similarly, the word "another" may mean at least a second or more.

[0019] As used in this specification and claim(s), the words

"comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0020] The term "about" is used to indicate that a value includes an inherent variation of error for the device or the method being employed to determine the value.

[0021] It is to be understood that the expression "hook block" used herein and in the appended claims is to be construed as any element that may be mounted at the free end of a hoist cable, including a conventional hook block.

[0022] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non- restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings.

[0023] Generally stated, the upper hoist limiter described herein includes a relatively heavy body that is suspended to the upper portion of a boom of a crane by at least one chain. The hoist cable of the crane is encircled by the body of the upper hoist limiter but is free to slide therein. When the hook block provided at the end of the hoist cable contacts and lifts the body, the tension is removed from the chain and the state of a switch, enclosed in the body, changes. This change of state causes a signal to be supplied to the crane operator so as to stop the upward movement of the hook block. [0024] Figure 2 of the appended drawings illustrates an upper hoist limiter 10 mounted to a hoist cable 12. A chain 14 and a bracket 16 are used to mount the body of the upper hoist limiter 10 to the boom of a crane (not shown). The chain 14 supporting the upper hoist limiter 10 can be as long as required, provided that it can support the weight of the assembly, including the accelerations due to its movements. The chain 14 has a first end connected to the bracket 16 and a second end mounted to the body of the upper hoist limiter 10.

[0025] Turning now to Figure 3, the upper hoist limiter 10 includes a body 18 housing the electronics as will be described hereinbelow. A hinged portion 20 of the body 18 can be open via a hinge (not shown) to install the body 18 about the hoist cable 12 as shown in Figure 2. A clevis pin 22 and a cotter pin 24 are used to removably secure the hinged portion 20 to the body 18. A ring 26 is used to secure the chain 14 to the body 18. Of course, more than one ring such as 26 can be used. In other words, the body 18 so encircles the hoist cable as to allow the cable to slide therein.

[0026] The body 18 includes an electronics compartment cover 28 secured to the body by fasteners 32 and a battery compartment cover 30 secured to the body by captive fasteners 34. The electronics cover 28 includes an antenna 36 for communication with a base station that may be installed in the crane cab (not shown) so as to be accessible by the crane operator. The fasteners 34 are captive to the battery compartment cover 30 to prevent their loss in the field when the battery (not shown) has to be replaced.

[0027] Figure 4 illustrates the body 18 without the covers 28 and 30 that respectively close an electromachanical components compartment 38 and a battery compartment 40. Weatherproofing seals such as silicone and O-rings (not shown) can be inserted in channels 42 and 44 to prevent the infiltration of the elements in the compartments 38 and 40 when they are closed by their respective covers 28 and 30. An aperture 48 provided on the top wall of the body 18 allows a rod to be inserted therein as will be described hereinbelow.

[0028] As can be seen from Figure 5, the battery compartment 40 receives a power source in the form of a battery 50 and the electromechanical compartment 38 receives the electronic and mechanical components 52 of the upper hoist limiter 10.

[0029] Figure 6 is a front elevation view of the upper hoist limiter 10.

[0030] Figure 7, which is a section of Figure 6, shows the electronic

54 and mechanical components 52 of the upper hoist limiter 10. More specifically, these components include a PCB 54 to which the antenna 36 is connected, a normally closed switch 56 connected to the PCB 54, a square piston 58 and a rod 60 to which the ring 26 is mounted and which is slidably inserted in the aperture 48. The rod 60 is also screwed in an opening of the piston 58 and secured with a set screw 62. A biasing element, in the form of a spring 64, is provided about the rod 60 and between the piston 58 and an upper wall 66 of the compartment 38.

[0031] The rod 60 may be slidably moved from a retracted position shown in Figure 7 and an extended position (not shown).

[0032] The spring 64 bias the rod 60 towards its retracted position shown in Figure 7 but is so selected that the weight of the body 18 is sufficient to overcome this bias action. [0033] The piston 58 has a square cross-section, thereby preventing its rotation in the compartment 38.

[0034] The PCB 54 is encapsulated in gel or epoxy 68 to prevent it from coming into contact with moisture. The PCB 54 includes a transmitter and the required electronic elements (not shown) to interface between the switch 56 and the antenna 36 to enable the switch state to be transmitted to the crane operator.

[0035] To prevent water or foreign matter from entering the electromechanics compartment 38 via the top aperture 48, a rubber boot 70 surrounds the rod 60. A sleeve 72 made of rugged material is used to protect the rubber boot 70.

[0036] The operation of the upper hoist limiter will now be described.

[0037] Figure 7 shows the upper hoist limiter in an alarm mode. This mode is actuated when the hook block (not shown) contacts the bottom portion of the body 18 and lifts it (see arrow 74). Indeed, when this is the case the weight of the body 18 is cancelled, i.e. that it is no longer supported by the chain 14. The rod 60 may thus move from the extended position (not shown) to the retracted position of Figure 7 under the biasing action of the spring 64 to place the piston 58 in the position illustrated in Figure 7. The normally closed switch 56 is thus placed in its closed state and an emitter circuit provided on the PCB 54 sends a wireless alarm signal to the crane operator (not shown) via the antenna 36. In other words, the relative movement between the rod 60 and the body 18 changes the state of the switch 56 and a signal representing the state of the switch 56 is supplied to the crane operator. [0038] When the upper hoist limiter is in safe mode (not shown), the weight of the body 18 compresses the spring 64 between the piston 58 and the surface 66, thereby keeping the switch 56 in its open state. A safe signal is sent to the crane operator and operation of the crane can continue undisturbed.

[0039] The body 18 is made of relatively heavy material such as, for example cast iron. Of course, any other suitably heavy and strong material can be used.

[0040] It is to be noted that the chain 14 could be replaced by other flexible member such as a cable. Similarly, more than one chain or other flexible member could be used.

[0041] Figures 8 and 9 illustrate second and third illustrative embodiments of upper hoist limiters that can accommodate different hoisting cable size. The body and electronics of these limiters is the same as described hereinabove and will therefore not be repeated for concision purpose.

[0042] More specifically, Figure 8 illustrates an upper hoist limiter

100 designed to receive fast-lines and whip-lines hoisting cable in an octogonal enclosure 102 provided with a hinge 104. A second ring 106 is provided to mount a second chain (not shown) thereto for balancing purpose. Of course, the shape of the enclosure 102 could be different than the octogonal shape illustrated in Figure 8.

[0043] Figure 9 illustrates an upper hoist limiter 200 designed to receive multiple lines hoisting cable (not shown) between four rollers 202. Again, second ring 204 s provided to mount a second chain (not shown) thereto for balancing purpose. [0044] It will easily be understood to those skilled in the art that the upper hoist limiters described hereinabove share the following features:

[0045] - When the hoisting cable moves up or down, the upper hoisting limiter stays at the same position;

[0046] - No pivot is necessary for the chain attachment, the chain is simply installed between an aperture of the bracket 16 and the ring 26;

[0047] - The chain attachment bracket 16 has holes compatible with common mounting bracket provided on crane booms;

[0048] - The chain attachment bracket 16 can simply be welded on a flat surface of the crane boom;

[0049] - The removable covers 38 and 40 close the compartments to protect the electronics and mechanisms from the element but also allow the electronics and mechanisms to be serviced in the field or at a repair center;

[0050] - All major electronics and mechanical components can be serviced in the field with simple tools;

[0051] - The electronics can be replaced by removing the electronics cover 28 and the switch 56 and replacing them with operational parts;

[0052] - The battery 50 can be replaced in the field by removing the cover 30 restricting the access to the battery only; [0053] - The replaceable antenna 36 is screwed on the electronics cover 28 and can be replaced with simple tools if damage to it should occur; and

[0054] - All changes to the alarm signals are transmitted by the means of a radio signal to a base station. The base station can lockout the hoisting mechanism.

[0055] As will easily be understood by one skilled in the art, the PCB

54 could include some alarm features sending information to the crane operator, for example, when the state of the battery is low or when the operation of the power circuit is compromised.

[0056] It is to be noted that the bracket 16 could be replaced by one of the links of the chain 14, for example to be welded to the boom of the crane.

[0057] It is also to be noted that the spring 64 could be absent from the body 18, therefore relying solely on the weight of the body 18 to change the state of the switch 56. Of course, one skilled in the art will understand that proper lubrication is required between the rod 60 and the aperture 48 to limit the sliding resistance therebetween.

[0058] Even though a mechanical switch 56 is shown in the drawings and described hereinabove, it is to be understood that other types of switch could be used, as long as it is adequate to detect the sliding movement of the rod 60 in the aperture 48. As a non-limiting example, Hall Effect sensors could be used. Therefore, the expression "switch" should be construed herein as any element that may detect the position of the rod 60 with respect to the body 18. [0059] It is to be understood that the invention is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The invention is capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the present invention has been described hereinabove by way of illustrative embodiments thereof, it can be modified, without departing from the spirit, scope and nature of the subject invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An upper hoist limiter to be mounted between the boom of a crane and a hoist cable, the hoist cable supporting a hook block, the upper hoist limiter including: a bracket so configured as to be mounted to the boom; a chain having a first end mounted to the bracket and a second end; a body mounted to the second end of the chain; the body being so configured as to encircle the hoist cable so as to allow the hoist cable to slide therein; the body including:

- a switch so interposed between the body and the rod that a) when the weight of the body is supported by the chain, the switch is in a first state and b) when the weight of the body is lifted by the hook block, the switch is placed in a second state by the relative movement between the body and the rod; wherein the state of the switch is supplied to an operator of the crane.

2. An upper hoist limiter as recited in claim 1 , wherein the body includes a hinged portion so configured as to be reciprocately moved between an open and a closed position to allow the body to be mounted about the hoist cable.

3. An upper hoist limiter as recited in claim 2, wherein the hinged portion may be locked in the closed position via a locking mechanism.

4. An upper hoist limiter as recited in claim 1 , wherein the body includes spaced apart rollers so configured as to receive a multiple lines hoisting cable.

5. An upper hoist limiter as recited in claim 1 , wherein the rod includes a first end provided with a ring to which the second end of the chain is mounted, and a second end.

6. An upper hoist limiter as recited in claim 5, further comprising a piston removably mounted to the second end of the rod.

7. An upper hoist limiter as recited in claim 6, wherein the rod is so slidably mounted to the body as to move between an extended position when the weight of the body is supported by the chain and a retracted position when the weight of the body is not supported by the chain.

8. An upper hoist limiter as recited in claim 7, further comprising a biasing element so mounted between the body and the piston as to bias the rod towards the retracted position; the biasing element being so selected that the weight of the body is sufficient to overcome the biasing action of the biasing element.

9. An upper hoist limiter as recited in claim 1 , wherein the switch is a mechanical switch.

10. An upper hoist limiter as recited in claim 1 , further comprising a transmitter so connected to the switch as to wirelessly transmit the state of the switch.

11. An upper hoist limiter as recited in claim 10, further comprising an antenna associated with the transmitter.

12. An upper hoist limiter as recited in claim 10, wherein the transmitter is mounted to a PCB and encapsulated in a weatherproofing gel.

13. An upper hoist limiter as recited in claim 12, wherein the PCB and the switch are enclosed in a first compartment of the body.

14. An upper hoist limiter as recited in claim 13, wherein the body further includes a second compartment configured to receive a power source.

15. An upper hoist limiter as recited in claim 14, wherein the first and second compartments are closed by separate covers.

16. An upper hoist limiter as recited in claim 15, further comprising weatherproofing seals provided between the separate covers and the body.

17. An upper hoist limiter as recited in claim 1 , further comprising a rubber boot surrounding the rod to weatherproof the aperture through which the rod is slidably inserted in the body.

18. An upper hoist limiter as recited in claim 17, further comprising a sleeve enclosing the rubber boot to provide protection thereto.

19. An upper hoist limiter to be mounted between the boom of a crane and a hoist cable, the hoist cable supporting a hook block, the upper hoist limiter being mounted to the boom via a chain having a first end mounted to the boom and a second end, the upper hoist limiter including:

a body configured as to encircle the hoist cable so as to allow the hoist cable to slide therein; the body including:

20. An upper hoist limiter as recited in claim 19, wherein the body includes a hinged portion so configured as to be reciprocately moved between an open and a closed position to allow the body to be mounted about the hoist cable.

21. An upper hoist limiter as recited in claim 20, wherein the hinged portion may be locked in the closed position via a clevis pin.

22. An upper hoist limiter as recited in claim 19, wherein the body includes spaced apart rollers so configured as to receive a multiple lines hoisting cable.

23. An upper hoist limiter as recited in claim 19, wherein the rod includes a first end provided with a ring to which the second end of the chain is mounted, and a second end.

24. An upper hoist limiter as recited in claim 23, further comprising a piston removably mounted to the second end of the rod.

25. An upper hoist limiter as recited in claim 24, further comprising a biasing element so mounted between the body and the piston as to bias the rod towards the retracted position; the biasing element being so selected that the weight of the body is sufficient to overcome the biasing action of the biasing element.

26. An upper hoist limiter as recited in claim 19, wherein the switch is a mechanical switch.

27. An upper hoist limiter as recited in claim 19, further comprising a transmitter so connected to the switch as to wirelessly transmit the state of the switch.

28. An upper hoist limiter as recited in claim 27, further comprising an antenna associated with the transmitter.

29. An upper hoist limiter as recited in claim 27, wherein the transmitter is mounted to a PCB and encapsulated in a weatherproofing gel.

30. An upper hoist limiter as recited in claim 29, wherein the PCB and the switch are enclosed in a first compartment of the body.

31. An upper hoist limiter as recited in claim 30, wherein the body further includes a second compartment configured to receive a power source.

32. An upper hoist limiter as recited in claim 31 , wherein the first and second compartments are closed by separate covers.

33. An upper hoist limiter as recited in claim 32, further comprising weatherproofing seals provided between the separate covers and the body.

34. An upper hoist limiter as recited in claim 19, further comprising a rubber boot surrounding the rod to weatherproof the aperture through which the rod is inserted in the body.

35. An upper hoist limiter as recited in claim 34, further comprising a sleeve enclosing the rubber boot to provide protection thereto.