TECHNICAL FIELD

This invention relates generally to single line material handling grapples and, more specifically, to a single line grapple that can controlledly release a load while the load is suspended in the air without any shock load to the crane.

PACygRpyp ART

Single line grapples are known in the art and find application most often in maritime loading and unloading operations. See U.S. Patent 4,807,918 to Weeks. Because this type of grapple must, by definition, operate from a single line, the prior art grapples have certain limitations which seriously reduce their efficiency. For example, when a load is release while suspended in the air, the crane is subject to a sudden and severe impulse shock or jerking motion. This impulse shock has two causes. One cause originates from the tines being flung open when the load is released. The second results from the manner in which a grapple operates. When a grapple picks up a load, the tines rarely completely close due to the bulky nature of the load material. Since the tines can not fully close, the two sheaves or pulley blocks within the grapple can not come completely together and a gap remains between the upper and lower sheaves. When the load is released, the gap is very quickly closed and the sheaves come together with great force, imparting a severe impulse shock to the crane. Repeated exposure to this force, caused by the up to 14 tons

weight of the grapple, is very likely to cause extensive damage to the crane.

The prior art in the grapple area has had limited success in controlling the tines' opening rate and thus minimizing the jerking motion. The above mentioned Weeks patent discloses the use of force dampening pistons connected between the top and bottom blocks of the grapple. While this prevents the tines from being flung open, it does not prevent the sheaves from being violently forced together. The jerking motion induced by the sheaves alone is great enough to expose the crane to unacceptable levels of stress.

The problem of gripping members being flung open has also been encountered in the area of single line clam shell buckets. While there has been some success in controlling the rate at which the two halves of the bucket open, see U.S. Patent 4,381,872 to Hahn, no method has been disclosed for dampening the impact of the sheaves. This is because the bucket art is not faced with the problem of impacting sheaves. Typically, buckets are involved in loading loose materials such as grain or gravel. Working with these types of materials, the bucket halves are able to fully close. Therefore, the sheaves operating the buckets come completely together. Thus, when the load is released, there is no violent collision between the sheaves. As a result of this heretofore unresolved problem, single line grapples were required to rest the materials being carried on the surface where the materials were to be deposited before the materials could be released. If the

materials were to be deposited in a truck bed or other place on which the grapple could not be safely or practically rested, then the materials had to be deposited on an alternative surface and another means used to place the materials in the desired place.

Clearly, a single line grapple that could release a suspended load of materials directly onto the desired platform without causing the sheaves to be violently forced together, and thereby reducing stress on the crane, would immensely increase the efficiency of the unloading operation and reduce damage to the crane.

Additionally, since no sufficient dampening mechanism existed in prior art grapples such that releasing a suspended load was practical, no releasing or tripping mechanism has been heretofore developed to initiate the opening of the tines while the grapple was suspended above the ground. DISCLOSURE OF INVENTION

Therefore, it is an object of this invention to provide a single line grapple that may release a suspended load in a controlled manner which substantially reduces the impulse shock to the crane caused by the sheave assemblies when a load is released.

It is another object of this invention to provide a tripping mechanism that may be remotely activated. Other objects and advantages of this invention shall become apparent from the ensuing description.

Accordingly, a single line grapple is provided comprising an upper block, a plurality of arms connected at

one end to the upper block and at an opposite end to a corresponding tine. The tines are pivotally connected to a lower block such that relative vertical movement between the blocks, opens and closes the tines. An upper sheave assembly is connected to the upper block and a lower sheave assembly is operatively connected to the upper sheave assembly by a cable. A remotely activated device is provided for engaging or releasing the lower block from the lower sheave assembly depending on whether it is desired that the tines be opened or closed. The grapple further has a hydraulic dampening device between the lower block and the lower sheave assembly to control the rate the tines open and the rate the sheave assemblies impact.

DESCRIPTION PF THE DR I GS 7IG. 1 is a three quarter perspective view of one of the preferred embodiments of the grapple.

FIG. 2 is a side view of the grapple of Figure 1 with the lower sheave assembly disengaged.

FIG. 3 is a side view of the grapple of Figure 1 with the lower sheave assembly engaged.

FIG. 4 is a side view of the grapple of Figure 1 in a substantially closed position.

FIG. 5 is a three quarter perspective view of a preferred engagement mechanism in connection with the lower sheave assembly and the lower block.

FIG. 6 is a three quarter perspective view of a preferred hook assembly of the engagement mechanism.

FIG. 7 is a side view of the engagement mechanism of the present invention operating in conjunction with the hook assembly and the pin.

FIG.8 is a schematic view of the hydraulic assembly and hydraulic system of the locking mechanism of the present invention.

FIG. 9 is a side view of the engagement mechanism of the present invention showing the engagement mechanism in the locked position. FIG. 10 is a side view of the engagement mechanism of the present invention showing the hook assembly deflecting the roller member during disengagement.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, the skeleton of the grapple comprises upper block 1 which is slidably connected to lower block 2 by guide tubes 4B and guide rods 4A. Apertures 25 are provided in upper block 1 through which guide rods 4A may extend when upper block 1 and lower block 2 move together as described herein below. The grasping mechanism is made up of a plurality of arms 5 each having an end pivotally connected to upper block 1. Tines 6 are claw shaped and have an end pivotally connected to lower block 2. An opposite end of each of arms 5 is pivotally connected to the back of a corresponding tine 6. Hydraulic cylinders 3B and hydraulic rams 3A are provided to dampen the relative movement of lower block 2 and lower sheave assembly 12, and thus the opening of tines 6.

It can be seen that relative vertical movement between upper block 1 and lower block 2 opens and closes tines 6. The aforementioned mechanism is well known in the art and has been employed for double line grapples. Those with skill in the art can modify the configuration of arms 5 and tines 6 so that the points of attachment vary. The key aspect of the grasping mechanism is that it opens and closes in response to relative vertical movement between upper block 1 and lower block 2. Upper block 1 and lower block 2 are drawn together by cable 7, which has two ends hanging from a single yoke 8. Each end of cable 7 is looped around lower sheaves 9 and up around upper sheaves 10. Cable 7 is reeved between lower sheaves 9 and upper sheaves 10 enough times to obtain the desired mechanical advantage. Those with skill in the art may substitute other guides for cable 7. For example, instead of a cable, rope could be used.

In a preferred embodiment of the invention, the sheaves 9 and 10 are rotatably mounted in sheave assemblies. Thus, upper sheaves 10 are part of upper sheave assembly 11 which is fixedly connected to upper block 1. Likewise, lower sheaves 9 are part of lower sheave assembly 12. But, rather than being fixedly attached to lower block 2, lower sheave assembly 12 travels on guide rods 4λ. Lower sheave assembly 12 has an engagement mechanism to engage lower block 2 which will be discussed in detail below. Additionally, at the desired time, lower sheave assembly 12 may be disengaged from lower block 2.

The mechanism to engage and disengage lower sheave assembly 12 and lower block 2 allows the grapple to operate from a single suspension line 13. The process by which the grapple closes about and lifts material is illustrated in FIGS. 2-4. FIG. 2 shows lower sheave assembly 12 disengaged from lower block 2. The weight of lower block 2 causes it to slide downward away from upper block 1. As the relative distance between upper block 1 and lower block 2 increases, tines 6 are spread open. The weight of the grapple is supported by cable 7 which in turn causes lower sheave assembly 12 to be drawn up into contact with upper sheave assembly 11. A bumper 14 is interposed between the assemblies to cushion any contact. Alignment of lower sheave assembly 12 is maintained by guide sleeves 16 fixedly attached to the sides of lower sheave assembly 12. Guide sleeves 16 are slidable on guide rods 4A. Additionally, guide tubes 4B and guide rods 4λ help align upper block 1 and lower block 2.

Once tines 6 are open, the grapple can be lowered onto material to be raised as shown in FIG. 3. At this time it is possible to engage lower sheave assembly 12 and lower block 2. Yoke 8 is lowered to provide slack in cable 7. The weight of lower sheave assembly 12 takes up the slack in cable 7 thereby dropping lower sheave assembly 12 onto lower block 2. The mechanism by which lower block 2 is engaged will be discussed below. It is sufficient to understand at this point that in a preferred embodiment, the engagement can be accomplished by any physical structure by which the weight

of lower sheave assembly 12 presses downward against lower block 2.

In FIG. 4, yoke 8 is raised with lower sheave assembly 12 and lower block 2 engaged. As cable 7 is drawn taut, upper block 1 and lower block 2 are drawn toward one another, thereby closing tines 6 as much as the bulky nature of the material will allow. As explained above, some space typically remains between lower sheave assembly 12 and upper sheave assembly 11, but tines 6 are relatively closed. The material can be released and tines 6 opened by disengaging lower sheave assembly 12 and lower block 2. Once lower block 2 is disengaged, it can be seen that the weight of lower block 2 as well as the weight of the material pressing outward on tines 6 will tend to open tines 6. To prevent tines 6 from being flung open and causing lower sheave assembly 12 to forcefully impact upper sheave assembly 11 as it moves quickly upward, the relative movement of lower block 2 and lower sheave assembly 12 is slowed by a pair of hydraulic dampening assemblies comprising hydraulic ram 3λ and hydraulic cylinder 3B. While FIGS. 2-4 show only one such assembly, both can be clearly seen in FIG. 1.

The end of the hydraulic ram 3 extending from the hydraulic cylinder 3B is pivotally attached to lower block 2. As can be seen more clearly in FIG. 1, the end of the hydraulic ram 3A is pinned at point 22 to the lower block 2 by any conventional pinning device. The hydraulic cylinder 3B may be connected by clamps, bolting, welding or any other conventional device or arrangement to lower sheave assembly

12. In the depicted embodiment, a dampening sleeve 15 is fixed to the hydraulic cylinder 3B and the dampening sleeve 15 is then welded to the side plate 52 of the of lower sheave assembly 12. Still viewing FIG. 1, hydraulic fluid reservoirs 17 are positioned above the hydraulic cylinders 3B and attached to the sides of the guide tubes 4B. A means of transferring the hydraulic fluid, such as hoses 20, connects the hydraulic cylinders 3B to the reservoirs 17. As best seen in FIG. 5, metering valve 18 allows the rate at which fluid flows from the hydraulic cylinder 3B to be adjusted. This flow rate thereby controls the rate at which the lower block 2 moves relative to the lower sheave assembly 12 and thus, the rate at which the tines 6 open. To selectively secure and release lower block 2 and lower sheave assembly 12, the invention employs an engagement mechanism. A preferred embodiment of the engagement mechanism of the present invention is shown in FIGS. 5-11. FIG. 5 illustrates a preferred engagement mechanism in connection with the lower sheave assembly 12 and the lower block 2. The engagement mechanism comprises: a hook assembly, generally indicated by the numeral 42; a biasing device, generally indicated by the numeral 44; a pin assembly, generally indicated by the numeral 46; and an engagement retaining assembly, generally indicated by the numeral 48.

In this preferred embodiment, the lower sheave assembly

12 has the hook assembly 42 pivotally mounted on each of its side plates 52. Hook assembly 42, more clearly shown in FIG.

6, includes two hooks 54 rigidly connected by a rigid retaining bar 56 and a slide plate 58 extending from the rigid retaining bar 56. Biasing device 44 is shown connected to hook assembly 42. As can be seen in FIG. 7, the slide plate 58 is the portion of hook assembly 42 which contacts the engagement retaining assembly 48, thereby preventing the hook assembly 42 from rotating out of contact with pin 64 of pin assembly 46. Each of hooks 54 also has a hook surface 60 adapted for engagement with a pin surface 62 of the pin 64.

As also shown in FIG. 7, the hook surfaces 60 are smooth planar surfaces disposed at an angle, α, from a line "L" perpendicular to the hook assembly's 42 axis of rotation. Angle α may be any angle which will generate a disengaging rotational force against the hook assembly 42 when the hook assembly 42 is not locked in engagement, and will provide vertical force to the lower block 2 when the hook assembly 42 is locked in engagement. In this preferred embodiment, α is about 30 degrees. The pin surface 62 is also a smooth planar surface. The pin surface 62 is disposed at an angle which will allow a planar portion of the hook surfaces 60 to contact a planar portion of the pin surface 62. As illustrated in FIG. 5, hook stops 66 are provided on each of the side plates 52 of lower sheave assembly 12. As better seen in FIG. 7, the hook stops 66 position the hooks 54, under the force from the biasing device 44, such that the hooks 54 are deflected around pin 64 during engagement of the lower sheave assembly 12 and the

lower block 2. In this preferred embodiment, biasing device 44 consists of shock absorbers 68 connected between the hooks 54 of hook assembly 42 and each of the side plates 52 of the lower sheave assembly 12. The shock absorbers 68 have sufficient pulling strength to keep the hook assembly 42 biased against the hook stops 66 but are sufficiently resilient to allow the hook assembly 42 to be deflected around pin 64 in use.

As most clearly seen in FIG. 6, the pin assembly 46 of this preferred embodiment includes two brackets 70. A pin 64 is connected between the two brackets 70. The two brackets 70 are spaced apart a distance sufficient to allow the hooks 54 to be received between the two brackets 70.

Shown in FIG. 5 is a preferred engagement retaining assembly 48 with the lower sheave assembly 12 engaging the lower block 2. The engagement retaining assembly 48 comprises: two brackets indicated by the numeral 74; a holding member, generally indicated by the numeral 76, and a locking mechanism, generally indicated by the numeral 78. The brackets 74 in this preferred embodiment are constructed of two metal plates attached perpendicular to the upper surface of the lower block 2. Referring again to FIG. 7, the brackets 74 are positioned a distance "A" away from pin 64. The distance λ must be sufficient to allow the hook assembly 42 to pass between the pin 64 and the brackets 74, but not so great that the holding member 76 cannot operatively contact slide plate 58 of the hook assembly 42. The term "operatively contact" means physically contact the

hook assembly 42 either directly or indirectly such as through an intermediate part.

This preferred embodiment includes such an intermediate part in the form of a roller member 86. The roller member 86 is mounted on axle 90 and positioned to contact the slide plate 58 of the hook assembly 42. The axle 90 extends outwardly from the roller and is mounted within a guide 92 (described below) which guides the roller member 86 toward and away from the hook assembly 42 when in use. The bracket plates 74 are rigidly connected together with connecting pins 106 and 105, which also connect brackets 74 with the holding member 76 and the locking mechanism 78, respectively. Each bracket 74 also includes an elongated guide 92. The guides 92 are adapted to slidingly receive one end of the axle 90 of the roller member 86. When the brackets 74 are mounted to the lower block 2 and each end of the axle 90 is received within a guide 92, the roller member 86 is free to both rotate about its center of rotation and to move in a direction toward and away from the hook assembly 42. The holding member 76 in this preferred embodiment is constructed of two metal pivot plates 98. The pivot plates 98 are rigidly connected by connecting pins 106 and 108. Connecting pin 106 extends out past the holding member 76 and pivotally connects the holding member 76 between the brackets 74. Connecting pin 108 pivotally connects of the locking mechanism 78 between pivot plates 98.

In a preferred embodiment, the locking mechanism 78 comprises a hydraulic cylinder 110; a hydraulic ram 112; a

hydraulic fluid reservoir 114 (shown in FIG. 5) ; a biasing means 116; and a valve 118 (shown in FIG. 8), controllable by an operator. Still referring to FIG. 7 , the hydraulic cylinder 110 and hydraulic ram 112 form the hydraulic assembly 120. One end of the hydraulic assembly 120 is pivotally attached to connecting pin 108 of holding member 76 and the other end is pivotally attached to the brackets 74 by connecting pin 105. The biasing means 116 is included to urge the hydraulic assembly 120 to either collapse or expand in length. Although it is possible to allow the weight of the hydraulic ram 112 to perform this task, in this preferred embodiment, a spring 117 is installed within the hydraulic cylinder 110 to bias the hydraulic ram 112 outwardly. It is, however, contemplated by the invention that other means for urging the hydraulic assembly 120 to collapse or expand may be used such as connecting a spring between the holding member 76 and the brackets 74 or using hydraulic fluid under pressure.

In this configuration, movement of the hydraulic ram 112 within the hydraulic cylinder 110 causes the holding member 76 to pivot about connecting pin 106. This pivoting action allows the holding member 76 to contact the hook assembly 42 during operation. Fig. 8 is a schematic view of the remote control arrangement that can be used to engage the locking mechanism 78. Movement of the hydraulic ram 112 within the hydraulic cylinder 110 requires that hydraulic fluid move between the hydraulic cylinder 110 and the hydraulic fluid reservoir 114. The movement of hydraulic fluid between the

hydraulic cylinder 110 and the hydraulic fluid reservoir 114 is controlled by the valve 118. The hydraulic assembly 120 is locked when the valve 118 is in the closed position and is unlocked when the valve 118 is in the opened position. In this preferred embodiment the valve 118 is a two position solenoid controlled valve.

Positioning of the valve 118 into the opened position is controlled by the operator via a radio link between a portable radio transmitter 122 and a portable radio receiver 124. The radio receiver 124 has an output port 126 controllable by the radio transmitter 122. The output port 126 is connected electrically to the dual solenoid 128 of the valve 118. Valve 118 is selectably opened by an operator using the radio transmitter 122. Positioning of the valve 118 into the closed position is controlled automatically by any means which will detect that the hook assembly 42 is engaged with the pin assembly 46. In this preferred embodiment, an electric circuit 121 is electrically connected to the dual solenoid 128. Electric circuit 121, which includes a proximity switch 123 mounted to the top of the lower block 2 beneath the pin 64 of the pin assembly 46 (as shown in FIG. 7) , is used to detect when the hook assembly 42 and the pin 64 are engaged. A proximity switch 123 suitable for use is available from Turk, Inc., Minneapolis, Minnesota under the part no. BI15-CP40-VN4X. When engagement is detected, the valve 118 is automatically positioned, by electric circuit 121 into the closed position - locking the hydraulic assembly 120. Automatically locking

of the hydraulic assembly 120 prevents damage to the engagement mechanism caused by premature locking of the hydraulic assembly 120.

FIGS. 7 and 9-10, illustrate operation of the preferred embodiment of the engagement mechanism. In Fig. 7 , the hook assembly 42 is shown as it would appear when advancing downwardly toward the pin 64 and valve 118 (not shown) is in the opened position. As the hooks 54 contact the pin 64, the weight of the lower sheave assembly 12 generates a force causing the hooks 54 to be deflected by the pin 64 in a direction opposite of that urged by the shock absorbers 68. As the hooks 54 continue downward, the slide plate 58 contacts and deflects roller member 86 causing holding member 76 to pivot about connecting pin 106. This pivotal movement causes the hydraulic ram 112 to move within the hydraulic cylinder 110. This is possible because the valve 118 is in the opened position.

Once the tips 130 of hooks 54 have passed the pin 64, the shock absorbers 68 cause the hooks 54 to rotate into the position shown in Fig. 9. When the hooks 54 are in this position, the slide plate 58 is no longer at its closest point adjacent to the brackets 74. This allows the spring 117 to push the hydraulic ram 112 downwardly in the hydraulic cylinder 110. This causes the holding member 76 to pivot, urging the roller member 86 against the slide plate 58. Once this has happened, the proximity sensor 123 is triggered and the valve 118 is automatically positioned by the electric circuit 121 into the closed position. This locks the

hydraulic assembly 120, thereby, locking the roller member 86 against the slide plate 58. The lower sheave assembly 12 and the lower block 2 are now engaged, allowing the tines 6 to be closed and the grapple lifted by tightening the cable 7 as shown in Fig. 4.

When the grapple has been moved to the desired location for emptying, the operator positions the valve 118, via the radio link, into the opened position to disengage the lower block 2 from the lower sheave assembly 12. The action of the engaging device during disengagement is illustrated in Fig. 10.

The force from the weight of the lower block 2 causes a downward force on the pin 64. This downward force is translated into a rotational force against hooks 54 by the angle of the engagement surfaces 60. This rotational force was previously resisted by the locked hydraulic assembly 120. However, once the hydraulic assembly 120 is unlocked by opening the valve 118, the rotational force is no longer prevented from causing the hooks 54 to pivot away from the pin 64. Once hook tips 130 clear the pin 64, the lower block 2 is disengaged from the lower sheave assembly 12. The tines 6 are now forced open by the weight of the lower block 2 and the load being carried.

Other means to releasably engage lower sheave assembly 12 and lower block 2 will become apparent to those with skill in the mechanical arts. Those means and of course obvious alternate embodiments and modifications to this

invention are intended to be included within the scope of the invention as defined by the following claims.