|Publication number||US3824578 A|
|Publication date||Jul 16, 1974|
|Filing date||May 22, 1972|
|Priority date||May 22, 1972|
|Publication number||US 3824578 A, US 3824578A, US-A-3824578, US3824578 A, US3824578A|
|Original Assignee||Harders H|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (18), Classifications (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Harders  July 16, 1974 ATTITUDE INDICATOR FOR LOAD LIFTING APPARATUS AND METHOD  Inventor: Holton G. Harders, 5521 E.
Highway 98, Panama City, Fla. 32401  Filed: May 22, 1972  Appl. No.: 255,707
 US. Cl 340/267 C, ZOO/61.52, 212/39 R, 340/282  Int. Cl. G08b 21/00  Field of Search 340/267 C, 282, 52 H, 272; 212/39 R; 180/104; 200/47, 61.52; 280/6 R  References Cited UNITED STATES PATENTS 3,236,535 2/1966 Barber ZOO/61.52 3,680,714 8/1972 Holmes 340/267 C 3,693,145 9/1972 Mize ZOO/61.52 3,713,129 l/l973 Buchholz 340/267 C Primary Examiner-John W. Caldwell Assistant Examiner-Glen R. Swann, lll
Attorney, Agent, or FirmBrowne, Beveridge, De- Grandi & Kline [5 7] ABSTRACT the tractor frame when the latter has undergone a predetermined unsafe amount of inclination. Any one of the switches upon closing will close a battery operated electrical circuit containing the alarm to sound the alarm. In another embodiment, the arm and switch assemblies are applied to an outrigger" jack system used to support the crane above the ground surface.
24 Claims, 14 Drawing Figures PATENIEDJUL 1 61914 SHEET 1 BF 4 HUM FATENTEU JUL 1 51974 saw a or 4 ATTITUDE INDICATOR FOR LOAD LIFI'ING APPARATUS AND METHOD BACKGROUND OF INVENTION In operating load lifting apparatus such as a crane, the underlying support frame of the crane is free to undergo inclination relative to the ground surface depending upon the position of the load being lifted or the inclination of the ground surface. For example depending on the weight of the load and its distance from the pivot point of the crane boom to the crane body, a moment can be exerted on the support frame causing the 1 support frame to tilt or move into an inclined position which if excessive can cause the crane and support frame to upset or turn over. Naturally the latter result can cause serious injury to personnel as well as damage to the load and crane apparatus. Inclination of the crane support frame can also result in cases where the crane support frame is resting on an inclined surface and the moment produced by the load being lifted, although insufficient to cause excessive tilting when the support frame is on a level surface, becomes sufficient to cause tilting when resting on an inclined surface.
Past and present attempts to avoid the above-noted problems have utilized various weight and/or angle gauges on the boom of the crane for indicating the weight being lifted and the angle of the boom. With this procedure, the crane operator is required to determine the weight of the load and the angle of the boom and then from a chart calculate the inclination of the support frame. Obviously this is avery cumbersome and error prone procedure particularly since it must be carried out as the load lifting operation proceeds.
Other efforts to provide an indication of the inclined attitude of the crane support frame have included complicated electronic devices which are expensive and in many cases unreliable.
OBJECTS OF THE INVENTION The present invention constitutes a novel method and apparatus for quickly and accurately determining an unsafe attitude of load lifting apparatus such as a crane. Included herein is such a method and apparatus which will clearly indicate an unsafe inclined attitude without requiring mental calculation or judgment on the part of the operator of the load lifting apparatus.
A further object of the present invention is to provide such a method and apparatus which are virtually foolproof and may be easily and economically implemented in standard or conventional load lifting apparatus such as tractor or wheel supported cranes where they will successfully function to indicate unsafe attitudes of the apparatus over long periods of repeated and rugged use.
SUMMARY OF INVENTION In summary, the above and other objects are achieved in connection with a crane supported on a frame which may be mounted on a tractor or an axle and wheel assembly, for ground travel. In the case of a tractor supported crane, a number of electrical switches are fixed on the support-frame at spaced locations for example two on each side with one adjacent the front end and the other, the rear end of the tractor. A plurality of switch actuating arms are mounted in association with the switches respectively for vertical movement relative to the frame when the frame tilts or inclines. If the tilt or inclination of the frame reaches a predetermined amount which is unsafe, the actuator arms will actuate the associated switches to close an electrical circuit and energize an alarm such as a buzzer or similar loud noise, which will indicate to the crane operator-the unsafe condition. The alarm circuit is incorporated on the tractor frame and may be suitably powered such as by battery.
With respect to cranes that are mounted on a frame suspended on a wheel and axle assembly, and wherein prior to use of the crane, the frame is raised by an outrigging system of jacks, the switch and arm assemblies of the present invention are incorporated on the base plates of the jacks. Should the frame incline to an unsafe degree causing one or more of the base plates to rise, the switch associated with the rising base plate, which switch is fixed to the base plate for movement therewith, will rise relative to the associated actuating arm to be engaged thereby thus closing the switch and sounding the alarm.
DRAWINGS Other objects and advantages of the present invention will become apparent from the following more detailed description taken in conjunction with the attached drawings in which:
FIG. 1 is a side view of a tractor mounted crane incorporating safety apparatus of the present invention, and showing a load lifted by the crane with the tractor in a stable level attitude;
FIG. 1a is a fragmental side view similar to FIG. 1 but showing the tractor in a forwardly inclined position;
FIG. 2 is an enlarged fragmental side view of the crane particularly illustrating the tractor portion thereof;
FIG. 3 is a cross sectional view taken generally along line 33 of FIG. 2 and illustrating the safety apparatus of the present invention when in a non-operating position such as when the tractor frame is in a stable or safe attitude as shown in FIG. 1;
FIG. 4 is a view similar to FIG. 3 but when the tractor support frame has moved into a dangerous inclined position, the view showing the safety device of the present invention in operation to sound an alarm;
FIG. 5 is an exploded perspective view of a portion of the safety apparatus of the present invention;
FIG. 6 is a side elevational view of the apparatus of FIG. 5 when mounted in the tractor and viewed for ex ample from the left hand side of FIG. 4 but with an associated housing removed;
FIG. 7 is a schematic view of the tractor illustrating an electrical alarm circuit and the positions of the safety apparatus of FIG. 5;-
FIG. 8 is a fragmental side view of a portion of a tractor frame and an associated endless track but incorporating a modified form of the safety apparatus of the present invention;
FIG. 9 is an end view of the apparatus shown in FIG. 8 but also showing in transverse cross section, the upper and lower runs of one of the endless tracks of the tractor;
FIG. 10 is a perspective view of a portion of an outrigger jack system for raising and lowering a crane such as may be supported on a wheel and axle assembly, and incorporating another modification of the present invention; and
FIG. 11 is a cross sectional view of safety apparatus embodying the present invention incorporated in the apparatus of FIG. and
FIGS. 12 and 13 are views similar to FIGS. 3 and 4 respectively but disclosing a preferred embodiment of the invention.
DETAILED DESCRIPTION Referring to the drawings in detail there is shown in FIGS. 1 and la for illustrative purpose only, a typical crane incorporating the present invention. The crane typically includes a boom 10 from which is suspended a cable 12 for lifting a load L; boom 10 being pivoted at 14 to body 16 for movement about a horizontal axis while being tied relative to body 16 through means of an articulated support system generally designated 18. Crane body 16 which contains the usual operators cab (not shown) from which the crane is operated, is mounted on a tractor'20 such as commonly referred to as a CATERPILLAR tractor, by means of a turntable 22 on which body 16 can rotate relative to the tractor about a vertical axis.
Trac'tor'20 typically includes a frame generally designated 24 having mounted thereto on opposite sides thereof, a pair of endless tracks 26 comprised of a series of linked pads 28 trained about opposite endsprockets 30 and 32. Sprocket 30 is a drive sprocket driven from the engine (not shown) through sprocket 31 and chain 31a as shown in FIG. 2 while sprocket 32 is an idler sprocket. Driving connection between sprockets 30 and 32 and endless tracks 26 is made by lugs or teeth 29 (see FIG. 3) formed on the inner side of each track pad 28 to engage the teeth on sprockets 30 and 32. Rotatably mounted on the undersides of frame 24 are a series of rollers 34 normally engageable on the inner sides of track pads 28 as shown in FIG. 3. Additional rollers 35 are rotatably mounted on the upper sides of support frame 24 to engage the upper runs of tracks 26 in conventional manner. The apparatus described above thus far is conventional and well known and therefore need not be described in greater detail, it being understood that the above-described apparatus itself forms no part of the present invention.
When the crane is operating in a stable attitude such as shown in FIG. 1, the tractor frame 24 is in a general horizontal plane with the frame rollers 34 engaging upon the lower runs of endless tracks 26. However should the load L be shifted for example too far forwardly of the tractor to cause an excessive moment to be exerted in a counterclockwise direction (as viewed in FIGS. 1 and la) on the tractor frame, the tractor frame will tilt forwardly downwardly moving into an inclined position as shown in FIG. la. Because of the inherent slack which exists between rollers 34 and endless tracks 26, frame 24 with rollers 34 thereon will move relative to endless tracks 26 with the result being a spacing designated d in FIG. la between rollers34 and the underlying run of endless tracks26.
In accordance with the present invention this displacement of tractor frame 24 which occurs relative to ground surface G or endless tracks 26 which remain on the ground surface regardless of the inclination of the frame, is employed to operate an electrical switch for energizing an alarm circuit for sounding an alarm when the inclination has reached an excessive, unsafe degree.
Hearing the alarm, the crane operator may immediv ately adjust the position of the load L to restorethe tractor to a stable attitude for example as shown in FIG. 1. I
The alarm circuit, schematically shown in FIG. 7, is incorporated in the tractor and includes an alarm 40 to be activated by any one of a number of switch assemblies 50 incorporated in the tractor frame as will be subsequently described in greater detail; there being end and open at its bottom end and being mounted by a plurality of elongated bolts 54 to the inner side walls of the tractor frame 24 in generally vertical position. Mounting bolts 54 pass through outwardly projecting lugs 55 on sleeve 52 and through spacer sleeves 56 located between mounting sleeve 52 and tractor frame 24 to space mounting sleeve 52 away from the side wall of tractor frame 24.
In the preferred form of the invention shown in FIGS. 12 and 13, the mounting assemblies 50 are mounted directly to frame side wall 24 at locations between two frame rollers 34. As will be described in greater details subsequently, each switch assembly 50 includes a bearing in the form of a roller 79. In the embodiment of FIGS. 3 and 4 this roller 79 engages the track pad 28 laterally outwardly of the lugs 29 as shown. However in the preferred embodiment of FIGS. 12 and 13, roller 79 engages the inner race 29a of track pad 28 as shown in FIGS. 12 and 13.
Adjacent the lower end of mounting sleeve 52 is an electrical switch 60 fixed thereto by means of screws 64 which pass through slots 62 in the switch housing; slots 62 serving to permit the position of switch 60 to be adjusted along the mounting sleeve 62 for purposes which will become apparent subsequently]. Electrical switch 60 has an upwardly facing contact 66 the depression of which will close the circuit shown in FIG. 7 to actuate alarm 40 when master switch 44 is closed.
Telescopingly mounted within mounting sleeve 52 is an elongated leg 70 having a rectangular cross section and being yieldably urged downwardly by a coil compression spring 72 received in the upper portion of mounting sleeve 52 with its upper end bearing against the top of mounting sleeve 52 and its lower end bearing against the top of leg 70 as best shown in FIG. 4. The
lower end of leg 70 is provided with a bearing means I such as roller 79 for. engagingthe upper or internal sides of the endless track pads 28 of the lower track runs.
For purposes of closing and opening switch 60, an actuator or control arm 74 which may be in the form of a fixed bolt or stud, is secured to an upper portion of leg 70 so as to project laterally therefrom through an elongated slot 75 formed in the external sidewall of mounting sleeve 52 as best shown in FIGS. 4, 5 and 6. In order to protect switch 60 and associated control arm 74 a casing 76 shown as having a box like configuration may be secured to the outer side wall of support sleeve 52 through screws passing through aperture 77 in the casing flanges and received in apertures 78 of support sleeve 52 as shown in FIG. 5.
In use during operation of the crane, when the latter is in a stable generally horizontal attitude such as shown in FIG. 1, spring 72 in support sleeve 52 will urge leg 70 downwardly so that its roller 79 will engage the upper or inner surface of endless track pads 28 as for example as shown in FIGS. 2, 3 and 6. In this condition of the tractor and switch assemblies 50, control arm 74'will be spaced from contact 66 of switch 60 as shown for example in FIGS. 3 and 6. However should the tractor frame 24 move into an inclined position relative to the ground surface G such as may be caused by a shift in the position of the load, or the weight of the load, or the ground surface being inclined or a combination of any of the latter three factors, certain of the frame rollers 34 will move upwardly away from the underlying pads 28 of the endless tracks 26 such as for example shown in FIG. la. Such displacement of frame 24 and rollers 34 relative to the endless tracks 26 will permit spring 72 of the adjacent switch assembly 50 to force the telescoping leg 70 downwardly. This .of course will bring control arm 74 closer to contact 66 of switch 60. The position of control arm 74 and switch contact 66 is calibrated so that upon inclination of the frame 24 to a predetermined degree which is dangerous or unsafe, the control arm 74 will move sufficiently to engage switch contact 66 to close switch 60 and thereby activate alarm 40 to indicate to the crane operator the dangerous attitude of the apparatus. The crane operator may then correct the weight distribution by changing the position of load L so as to restore frame 24 to a stable or less inclined attitude. This restoration movement of frame 24 will bring rollers 34 closer towards endless tracks 26 which will have the effect of retracting leg 70 into its support sleeve 52 therebydisent invention wherein the switch assemblies 50 are fixed to the tractor frame to overlie the central recesses in the frame rollers 34a so that rollers 79 of the switch 1 assemblies 50 engage the rollers 34a in the recesses engaging control arm 74 from switch contact 66 to I open the alarm circuit and deactivate alarm 40.
In order to calibrate the relative position of the control arm 74 and switches 60, to make it suitable for a particular crane operation, screws 64 mounting switches 60 to support sleeves 52 may be loosened and the switches 60 moved along support sleeve 52 by virtue of the slots 62 provided in the casing of the switches 60. When the desired spacing between the switch contact 66 and control arm 74 isachieved, screws 64 may be tightened to fix switches 60 in the desired position.
It will be seen from the above that the safety apparatus of the present invention is directly responsive to the change of attitude of the tractor frame 24 so that its operation is extremely sensitive and reliable. Furthermore, the safety apparatus of the present invention may be utilized to correct excessive longitudinal as well as transverse inclination of the track frame 24 since the four switch assemblies 50 spaced as shown and described will sense transverse as well as longitudinal inclinations of the tractor frame as well as diagonal inclinations. It should further be appreciated that switch assemblies 50 may be constructed from relatively simple but sturdy materials which are not subject to break thereof as shown in FIG. 9 under the bias of springs 72. In this modification however frame rollers 34a are mounted for vertical movement relative to tractor frame 24 by means of bearing blocks 80 which receive the shafts 34b of rollers 34a. Bearing blocks 80 in turn are fixed to elongated vertical bolts 82 mounted for vertical sliding movement relative in and to. tractor frame 24; the downward movement of the blocks 80 being limited by stops in the form of nuts 84 secured to the upper ends of bolts 82. Furthermore a pair of triangular plates 86 defining a vertical channel are secured to the undersides of frame 24 to receive and guide blocks 80 in their vertical movement.
During operation'of the crane when the latter is in a stable or relatively horizontal position such as shown in FIG. 1, rollers 34a will engage pads 28 in the lower runs of tracks 26 and switch assemblies 50 will be disengaged due to the spacing between control arms 74 and the associated switch contacts 66. However should the tractor frame 24 move into an excessively inclined position wherein frame 24 will move upwardly away from the ground surface G and the lower run of tracks 26, this will permit spring 72 of the switch assembly adjacent the upward displacement of the frame 24 to move the associated leg downwardly thus restoring engagement between frame rollers 34a and pads 28 of the tracks. Such movement of the leg 70 will cause control arm 74 to engage switch contact 66 which will energize the alarm 40 to indicate the dangerous attitude of the tractor frame. The downward movement of the leg 70 of the switch assembly will be permitted by virtue of the movable mounting of blocks which will move downwardly together with mounting bolts 82 under the guidance of plates 86.
Referring now to FIGS. 10 and 11 there is shown safety apparatus including switch assemblies 50a in ac-' cordance with the present invention used in connection with a crane (not shown) whose body 16 is mounted on a frame 90 which in turn is supported on an outrigger jack system generally designated 100. This type of crane may be normally supported, that is when not in use, on a wheel and axle assembly, (a portion of the wheel 102 being shown in FIG. 10) rather than a tractor support frame. Jacks'104 which themselves may be conventional are typically supported on base plates 106 which in turn rest on a beam 108 for load distribution purposes.
In accordance with the present invention, switch assemblies 50 a are installed on each base plate 106 with the mounting sleeve 52a being fixed such as by welding or otherwise to the upper surface of base'plate 106 as shown in FIG. 11. In the specific embodiment shown, the under side of base plate 106 is recessed at 110 to receive a bearing foot 74a fixed to the bottom of leg 70a of switch assembly 50a as shown in FIG. 11. Spring 72a in support sleeve 52a urges leg 70a downwardly into engagement with beam 108 as shown in FIG. 11.
Switch 60a of switch assembly 50a is secured to support sleeve 52a so that it is movable with baseplate 106. During stable attitudes of support frame 90 and outrigging system 100, the control arms 74a and switches 60a will be spaced from each other as shown in FIG. 11. However, should the support frame 90 and the outrigging system 100 shift into an inclined position sufficient to cause one or more of base plates 106 to rise above and separate from the underlying support beam 108, the support sleeve 52a will rise together with base plate 106 to thus cause switch 60a to approach the associated control arm 74a. In this embodiment, the control arm 74a will remain in a stationary location since the associated spring 72a will urge leg 70a downwardly to maintain engagement with beam 108. As the inclination of the support frame 90 increases and the displacement of sleeve 52a moving together with base plate 106 increases, switch 60a will move into contact with the associated control arm 74a to sound the alarm that the attitude .of the frame and out-rigger system is dangerous. The crane operator may then redistribute the load L being lifted to restore the support frame and outrigger system 100 to a stable condition where the base plates 106 engage the underlying beams 108 thus causing separation of the switch 60a and control arm 74a and deactivation of the alarm.
Although in FIG. 10, only one end section of the crane support system has been shown, it will be appreciated that the opposite end of the support system although not shown will contain the same safety switch assemblies 500 incorporated in the outrigger jack system at that end.
I claim: I
1. In a load lifting apparatus such as a crane mounted on a tractor including a support frame and a pair of endless tracks situated in side-by-side relationship; means for indicating a predetermined inclined position of said support frame including an indicator means capable of issuing a signal, a switch means, and a control arm associated with said switch means, one of said switch means and control arm being fixed with respect to said support frame for movement therewith and the other being mounted on said support frame for movement relative thereto such that when said support frame moves into said predetermined inclined'position the control arm will engage said switch means to energize said indicator means for issuing a signal, said switch means being connected to said indicator means to energize the same when engaged by said control arm, and wherein said switch means is fixed to said support frame to be movable therewith,and wherein there is further included spring means biasing said control arm downwardly.
2. The combination defined in claim 1 further including a support sleeve fixed to said support frame and having fixed thereon said switch means, a legtelescopingly received in said support sleeve having fixed thereon said control arm, said leg having a bearing means at its lower end engageable with the lower run of one of the endless tracks, and wherein said spring means biases said leg downwardly into engagement with said endless track.
3. The combination defined in claim 2 wherein said spring means is located in said support sleeve.
4. The combination defined in claim 3 wherein said spring means is a coil compression spring with one end engaged on the upper end of said leg and the other end of the spring engaged in an end wall of said support sleeve.
5. The combination defined in claim 4 wherein said support sleeve has an elongated slot in said one wall thereof and wherein said control arm projects through said slot externally of said support sleeve.
6. The combination defined in claim 5 wherein said switch means has means for adjusting its position along said support sleeve towards or away from said control arm.
7. The combination defined in claim 6 whereinsaid bearing means on said leg is a roller.
8. The combination defined in claim 7 further including a cover fixed on. said wall of said support sleeve to enclose said control arm and said switch means.
9. The combination defined in claim 1 further including a leg urged by said spring'means into engagement with the upper surface of the lower run of one of said endless tracks, said leg having fixed thereto said control arm.
10. The combination defined in claim 9 further including a support member fixed to said support frame and having fixed thereon said switch means, said leg being mounted on said support member for movement relative thereto.
track; means for indicatinga predetermined inclined position of said support frame including an indicator means capable of issuing a signal, switch means connected to said indicator means to energize the same upon actuation of the switchmeans, and switch actuating means associated with said switch means for actuating the same, one of said switch means and actuating means being fixed with respect to said support frame for movement therewith and the other being engaged on said traction means and also mounted to said support frame for movement relative thereto such that when said support frame moves into said predetermined inclined position the switch actuating means will engage said switch means to energize said indicator means for issuing a signal.
12. A combination defined in claim 11 wherein said switch: actuating means is engaged on the lower run of said endless track.
13. The combination defined in claim 12 wherein said endless track has a longitudinally extending race on which'said rollers are engaged and wherein said switch means is engaged on said race at a location between an adjacent pair of said rollers.
14. The combination defined in claim 11 wherein said switch actuating means is engaged on one of said rollers and wherein said one roller is mounted for vertical movementrelative to said support frame.
15. The combination defined in claim 11 wherein said switch means is fixed to said support frame for movement therewith, and wherein said switch actuat ing means includes an arm engageable with the switch means and a leg holding said arm and engaged on said traction means.
16. The combination defined in claim 15 wherein said leg contains bearing means at the bottom thereof engageable on the lower run of the endless track.
17. The combination defined in claim 16 further including a mounting sleeve fixed to said frame for movement therewith and having a passage slidably receiving said leg with the leg projecting from the bottom of the mounting sleeve and engaged on the lower run of said endless track.
18. The combination defined in claim 17 wherein said switch means is fixed to said mounting sleeve.
19. In combination with a tractor including a support frame and a pair of endless tracks situated in side-byside relationship; means for indicating a predetermined inclined position of said support frame including an indicator means capable of issuing a signal, a switch means, and a control arm associated with said switch means, one of said switch means and control arm being fixed with respect to said support frame for movement therewith and the other being mounted on said support frame for movement relative thereto such that when said support frame moves into said predetermined inclined position the control arm will engage said switch means to energize said indicator means for issuing a signal, said switch means being connected to said indicator means to energize the same when engaged by said control arm, and wherein said switch means is fixed to said support frame to be movable therewith and wherein there is further included spring means biasing said control arm downwardly, and a leg urged by said spring means into engagement with the upper surface of the lower run of one of said endless tracks, said leg having fixed thereto said control arm.
20. In combination with a load lifting apparatus having a support means supporting the apparatus on the ground surface during use; indicating means for issuing a signal indicating a predetermined amount of inclination undergone by the support means as'a result of load distribution on the apparatus, said indicating means including an alarm, switch means connected to the alarm to energize the alarm for issuing a signal when the switch means is actuated, a control arm for actuating the swith means, a sleeve associated with said support means to be movable therewith when the support means is inclined during use when the apparatus reand said support means when the support means is inclined during use when the apparatus receives a load, one of said switch and control arm being fixed to said sleeve for movement therewith and the other of said switch means and control arm being fixed to said leg for movement therewith such that when said support means moves into-a predetermined inclined position said control arm will engage said switch means to energize the alarm for issuing a signal.
21. The combination defined in claim 20 wherein said support means includes a tractor having a frame and a pair of endless tracks situtated in side-by-side relationship, a plurality of rollers mounted on said frame for engaging upper sides of lower runs of the endless tracks, means mounting said rollers for vertical movement relative to said frame, and wherein said leg is biased and engageable on said-rollers to urge the same towards the lower runs of said endless tracks.
22. The combination defined in claim 21 wherein there is provided four pairs of said switch means and control arm, two pair being associated with each endless track with one pair located adjacent the forward end of the endless track and the other pair located adjacent the rear end of the endless track.
23. The combination defined in claim 20 wherein said support means includes a jack means adapted to be mounted on the ground surface, and wherein said switch means, control arm, and sleeve are mounted in association with said jack means.
24. The combination defined in claim 23 wherein said jack means includes a base member adapted to rest on the ground surface or an underlying load distribution member resting on the ground surface, said base member member having an opening therethrough, said sleeve being fixed to and upstanding from the base member with the open bottom end of the sleeve communicating with the opening in the base member, and wherein said leg projects through the opening in the base member to be engageable on the ground surface or on an underlying load distribution member resting on the ground surface.
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|U.S. Classification||340/685, 200/61.52, 340/689, 212/277|
|International Classification||B66C23/90, B66C23/00|
|Cooperative Classification||B66C23/905, B66C23/90|
|European Classification||B66C23/90B, B66C23/90|