Abstract:
A light weight compact grappling hook which finds use in at least urban terrain comprising a small head member provided with a plurality of arms or blades which are serrated and/or provided with cutting surfaces/edges. The shaft which is connected to the head can be rigid or flexible. The flexible feature facilitates achieving a hold on surfaces which might otherwise be difficult. The arms or blades are each pivotally supported on pairs of pins and can be spread from folded storage positions and locked in position prior to deployment, or can be spring biased so that spreading and operative deployment is achieved en route to the target.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Provisional Patent Application Ser. No. 60/095,271 filed on Aug. 4, 1998, entitled COMPACT GRAPPLING HOOK PARTICULARLY ADAPTED FOR MILITARY/TACTICAL TYPE ENTRY/EXIT OPERATIONS IN URBAN TERRAIN. The content of this Provisional Patent Application is hereby incorporated by reference thereto. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to grappling hooks. More specifically, this invention relates to a grappling hook arrangement which is light, robust and which can be folded into a compact arrangement that can be readily transported to and from a site at which entry/exit use is desired. 
     2. Description of the Related Art 
     Under specialized conditions such as encountered in tactical operations such as Mounted Operations in Urban Terrain (MOUT), for example, the ability to be able to hurl a grappling hook up onto a roof or a high structure such as a building, tower or the like, is essential. However, currently available grappling hooks are heavy and cumbersome, and the entering/exiting of a site, such as a high building, can deteriorate into a debacle if there is a need to make multiple throws before a good hold is achieved. As will be appreciated, the above type of tactical operations require speed and stealth and the time needed to make a number of throws and to tolerate the noise produced by a throw which misses and clatters to the ground, can spell the difference between success and failure. 
     The ability to store the devices in a backpack or the like and to be able to carry this type of equipment to the site of use is also vital. Accordingly, the weight of a grappling hook must be small and the device highly compact to permit a person to carry it along with other equipment such as considerable lengths of rope, etc. However, the distribution of the weight is also important to ensure a good flight path after being propelled into the air. 
     A clear need for a lightweight, compact piece of equipment which can be hand thrown or fired from a launching device, therefore exists, especially under the above types of conditions. This need has not been satisfied by currently commercially available units. 
     SUMMARY OF THE INVENTION 
     The present invention is, in light of the above, directed to providing a light weight grappling hook which is suited for entry/exit of sites such as buildings, fences, towers and the like. 
     The present invention is further directed to providing a light weight grappling hook which can be folded into a compact arrangement suitable for easy transport to and from the site of use. 
     In addition to the above, the present invention is directed to providing a light weight grappling hook which can be fired from a device such as a grenade launcher, and which remains folded into its compact form until such time as it is in flight toward a target. 
     Still further, the present invention is directed to providing a light weight grappling hook which has blades which can be pivotally deployed from a folded state and which are shaped and/or serrated in a manner which provides maximum grip on surfaces such as concrete/steel and the like from which buildings are often made. 
     The present invention is also directed to providing a light weight grappling hook which has multiple applications and which can be fired or manually thrown to a target area and/or used to breach trip wires, antipersonnel and tilt-rod type anti-tank mines. 
     Additionally, the present invention is directed to providing a light weight grappling hook which has a flexible shaft and which facilitates getting good engagement even when the device does not have a 90° bite and which tends to eliminate the need to make second or third throws to obtain proper placement of the device. 
     In brief, in order to achieve the above objects a small head member is provided with a plurality of arms or blades which are serrated and/or provided with cutting surfaces/edges. A shaft which is connected to the head can be either rigid or flexible. In the case that the shaft is flexible, achieving a hold on surfaces which might otherwise be difficult, is facilitated. The arms or blades themselves are each pivotally supported on pairs of pins and can be spread from folded storage positions and locked in position prior to deployment, or can be spring biased so that spreading is achieved en route to the target. 
     More specifically, a first aspect of the invention resides in a grappling hook comprising: a head member; first and second pins; an arm pivotally mounted on the first pin, said arm being formed with a curved slot in which the second pin slides; and a shaft operatively connected with said head member. 
     The invention is further designed such that the head member is formed with a slot and wherein the arm has an end portion received in the slot, and wherein the head member has a manually operable locking device which allows the arm to be selectively locked in a predetermined position. 
     The invention further features biasing means for biasing the arm to pivot from a position wherein it is essentially parallel with the shaft, to a position wherein it is essentially perpendicular to the shaft. Another feature is that the shaft can be flexible and includes a connector at a lower end for connection with a rope or strap. 
     In instances where the invention is to be launched from a powered device, the arm can be provided with a hook member which is adapted to clip onto the mouth of a barrel of the launching device. 
     Another feature of the invention resides in the provision of an elastomeric sleeve which fits over a barrel of a device which launches the grappling hook toward a selected target. This sleeve has a toroidally shaped recess which extends about the barrel and which receives an end of the arm that is distal from the first and second pins and which retains the arm in a position wherein it is essentially parallel with the shaft until such time as the grappling hook is launched from the barrel. 
     In order to improve the grip and engagement on surfaces such as encountered in urban terrain, for example, the arm is provided with a plurality of serrations along a lower edge portion thereof. To complement this, the arm is provided with a first sharp cutting edge along an upper edge portion thereof to enable in-flight cutting of objects which are encountered along the way. In addition to the above, a second sharp cutting edge formed at a free end edge of the arm is provided, the first and second sharp cutting edges forming two sharp points which dig into surfaces engaged thereby. 
     A second aspect of the invention resides in a grappling hook comprising: a head member having a plurality of arm receiving slots; a plurality of arms respectively received in the plurality of slots, each of the arms having a round hole and a curved slot formed therein; a plurality of first and second pins, each of the first pins being disposed through a round hole formed in each of the arms, and each of the second pins being received in a curved slot formed in each of the arms, each of the slots being so dimensioned that when the arms assume a first folded position, each of the second pins is located at or proximate a first end of the respective slots, and when the arms are swung out from the first folded position to a second unfolded position, the second pins are located at or proximate a second end of the respective slots; and a shaft operatively connected with the head member, the shaft being rigid and flexible. 
     This second aspect, of course, also features locking means for locking the arms in their respective second unfolded positions. This locking means can also include a locking aperture formed in each of the arms. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and attendant advantages of the present invention will become more apparent as a description of the preferred embodiments is given with reference to the appended drawings in which: 
     FIG. 1 is a partially sectioned view showing a grappling hook according to a first embodiment of the invention; 
     FIG. 2 is a plan view showing the top of a head member which forms a vital part of the first embodiment; 
     FIG. 3 is a plan view of a locking device which can be used to lock the pivotal pawls or grappling arms (blades) of the first embodiment in an operative position; 
     FIG. 4 is a plan view of a variation of a locking device which can be used with the first embodiment of the invention; 
     FIG. 5 is a side view of a plastic coated wire cable which forms a flexible shaft which forms an important part of the first embodiment of the invention; 
     FIG. 6 is a side view showing a variation of the flexible shaft which can be used in connection with the first and/or other embodiments; 
     FIGS. 7 and 8 are respectively side elevation and plan views of an arm which can be used in connection with the first embodiment of the invention; 
     FIGS. 9,  10  and  11  are respectively side elevation, plan and end elevations of an arm which can be used in connection with the embodiments of the invention; 
     FIG. 12 is a top plan view showing another embodiment of the invention which has been formed of octagonal stock and which depicts the manner in which the bores in which the pins which operatively connect the arms to the main head, are drilled; 
     FIG. 13 is a front view of a shaft which can be used in connection with embodiments of the invention and which is provided with a screw thread at its upper end; 
     FIG. 14 is a top plan view of a head member of a further embodiment of the invention; 
     FIG. 15 is a side view of the head member shown in FIG. 14, depicting the provision of a spring receiving slot; 
     FIG. 16 is a view of a torsion spring which can be disposed in the spring receiving slot shown in FIG. 15, and which can be used to bias the arms of the invention out into operative positions; 
     FIG. 17 is a side view of a locking device which can be used with the embodiments of the invention; 
     FIG. 18 is a top plan view showing details of the locking device which is used with the key-like member which is shown in FIG. 17; 
     FIG. 19 is a top plan view of an embodiment of the invention which is provided with a locking device of the nature shown in FIGS. 17 and 18; 
     FIG. 20 is a side view of an arm which is adapted for use with the locking device depicted in FIGS. 17-19; 
     FIG. 21 is a partially sectioned side view of an embodiment which is adapted to be fired from a launching device and which features clip or catch members which engage the inner wall of the barrel of the launcher and which hold the arms of the grappling hook in a folded position; 
     FIG. 22 is a sectional side view showing a barrel of a launcher which can be used in conjunctions with the embodiments of the present invention and which is equipped with an elastomeric member adapted to retain the arms of the grappling hook in a folded position prior to being fired toward a target. 
     FIG. 23 is a top plan view of a three-bladed embodiment; 
     FIG. 24 is an exploded side sectional view showing the constructional details which are used to connect the shaft to the head portion of the device; 
     FIG. 25 is a side view of a variant of a blade which can be used with the embodiments of the invention and which has an angled portion which improves the grip on hard surfaces such as concrete and the like; 
     FIG. 26 is a side elevation of an arm which is similar to that shown in FIG. 7, but which is adapted for specialized use and is provided with a ball at the end to prevent the tip of the blade from digging into the ground; 
     FIG. 27 is a side elevational view of a further embodiment of the invention which features flat springs which are used to selectively maintain the arms in an extended operation position. 
     FIGS. 28A and 28B are respectively plan and elevational views showing the configuration of a “three-wing” head of the three bladed hook arrangement and socket head cap screws which are used to connect the arms or blades to the head; 
     FIG. 29 is a side view of a spring loaded pin/bolt arrangement which can be used with the arrangement shown in FIGS. 31 and 32; 
     FIG. 30 is a perspective view of second type of spring loaded pin/bolt which can alternatively be used with the arrangement shown in FIGS. 31 and 32; 
     FIG. 31 is an exploded view showing a further embodiment of the invention wherein the arms or blades are selectively maintained in place by means of spring loaded bolts which are disposed through a third set of openings formed in wing portions of the head; and 
     FIG. 32 is a perspective view showing the arrangement depicted in FIG. 31 in a fully assembled and ready to use configuration. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a first embodiment of the present invention. In this arrangement, a body or head  100  is provided with a plurality of pivotal blade-like pawls or arms  102 . The head  100  is formed with four slots  104  in the manner depicted in FIG.  2 . Each of these slots  104  receives the inboard end of the arms  102 . The head  100  is, in this instance, made from cylindrical stock and has upper and lower tapers or chamfers  100 A,  100 B, turned thereon. A through bore  100 C is formed coaxially through the head  100 . The upper end of the bore has two countersunk portions reamed therein while the lower end is provided with only one. 
     Each of the arms  102  is provided with a drill hole  102 A through which a first pin  106  is disposed and about which the arm  102  is pivotal. Each arm is further formed with an arcuate slot  102 B which is adapted to slidably receive a second pin  108 . In this embodiment, in addition to the two pin receiving apertures, each arm  102  is additionally provided with a locking aperture  102 C. These locking apertures  102 C are adapted to receive the locking pawls  110 A of a locking member  110  of the nature shown in FIG. 3, and which has a dished center portion  110 B which is adapted to seat in the second of the countersinks formed in the top of the head  100 . This locking member  110  is provided with upstanding tab members  110 C which are adapted to facilitate the manual manipulation of the locking member  110  between locked and un-locked positions. 
     As depicted on the right hand side of FIG. 1, when the arms are each pivoted from a storage position to an operative one, and the locking member  110  is rotated clockwise, each locking pawl  110 A engages in a locking aperture, thus preventing pivotal movement of the arms  102  back toward their storage positions. 
     A shaft member  112 , which in this embodiment is formed of steel cable (wire rope) which is encased in a plastic sheath, has a ball member  114  swaged at its upper portion and a swaged steel ring or the like  116  at the lower portion. As shown, when this shaft member  112  is disposed through the bore  100 C, the ball  114  can seat in a dished portion  110 B of the locking member  110 . By disposing one or more C rings  118  about the cable and forcing these into the recess defined by the countersink at the lower end of the through bore  100 C, and simultaneously pulling the shaft member  112  back through the through bore  100 C, the ball  114  is retained in its position in the dished portion  110 B of the locking member  110  and thus secures the locking member  110  in position. 
     The flexible cable which forms the shaft member  112  is, in accordance with the invention, of great utility, in that it permits the shaft to flex in a manner which permits the arms to bite in and take hold under conditions wherein, if the shaft were to be rigid, the arms  102  might be lifted out of engagement. More specifically, in the instance the grappling hook is used on a roof, for example, the traction which is applied to a rigid shaft might produce a moment which would lever the arms up and away from a position wherein good engagement was achieved, and thus force the need for repeated attempts to achieve a good hold. In other words, the flexibility of the shaft  112  permits it to curve over sharp right angle corners and the like and to apply tractive force about corners. 
     As will be appreciated, the first embodiment is simple and rugged. The provision of two pins  106 ,  108 , per arm increases reliability and, once in the lock position, the arms are effectively connected to the head member at three points, viz., the two pins and a locking pawl. 
     By way of example, the head  100  can be made of either chromalloy, steel, titanium or aluminum stock, which is milled/turned, and fitted with arms which are of the same material as the head. The length of the arms  102  is about 4.5 inches providing an overall span of about 10 inches when the hook is open. The overall length of the device when folded is between 9 and 12 inches and preferably has a weight of 1.5-3.0 lbs., and is sufficiently compact to be stored in a soldiers butt pack, for example. 
     In application, the hook can be inverted to allow gravity to move the arms  102  from their stored position to a full open condition, and the locking device  110  is manipulated to lock the arms  102  open. The device is then ready to hurl toward an intended target. 
     FIG. 4 shows an variant of the locking device shown in FIG.  3  and is  30  accordingly denoted by the numeral  110 ′. In addition to pawls  110 A′ and upstanding tabs  110 C′, this device is provided with a pair of arcuate slots  110 S′ which are adapted to have screws disposed therethrough. By boring and tapping two holes in suitable positions in the upper surface of the head  100 , it is possible to tighten the screws and set the resistance to rotation to a level suitable for ensuring that the movement from either of the locked or unlocked positions is resisted with a suitable amount of friction. 
     The present invention is not limited to climbing and can be used for tasks such as breaching trip wires, tripping anti-personnel mines and tilt-rod type anti-tank mines, for example. In this connection, as well as the climbing aspects of the invention, the arms which are used with the present invention can be provided with sharp cutting edges as well as points/serrations. The device can be fired through jungle to cut a path therethrough. Pulling the device back using a line or cable, facilitates further cutting and/or tripping of anti-personnel devices. 
     FIGS. 7 and 8 show an example of an arm design which can be advantageously used with the present invention. As will be essentially self-evident, the arm  102 ′ has tapered edges  102 K′,  102 L′ formed along the upper and tip edge portions which cooperate to form two sharp corners K and L. The underside is formed with sawtooth-like serrations  102 M′ which cut into and hold on relatively smooth surfaces such as are apt to be encountered in urban terrain. 
     FIGS. 9 to  11  show another example of arm configuration which can be used in connection with the embodiments of the invention. As will be appreciated, the illustrated arm is similar to that shown in FIGS. 7 and 8, but has a sharp cutting edge  102 P″ along the last portion of the upper edge. This edge  102 P″ can be used to sever wires and the like, for example, which are encountered in the flight of the hook toward its target. 
     FIG. 12 is a plan view of an embodiment of the invention wherein the head  200  is formed from octagonal stock and which demonstrates the manner in which the head is bored to permit the installation of the pins  206 ,  208  which are used to support the arms  204 . In this embodiment, as in all others, the pins  206 ,  208  are made of a material which is harder and more resistant to shearing than the remainder of the device and which can withstand considerable loads without deformation or loss of integrity. 
     FIG. 13 shows a rigid shaft arrangement. The upper end of this shaft  212  is tapped to form a screw thread  212 A which can be screwed into a tapped bore formed in the head in the manner shown in FIG. 21, for example, or passed through the head and engaged with a suitable member on the other side. 
     It is within the scope of the present invention to use arms which do not have locking devices and which are used in combination with biasing arrangements such as springs to bias the blades out toward their respective operative positions. This type of arrangement is of particular use when the hook is used in combination with a powered launching device such as a grenade launcher or the like. 
     FIGS. 14 to  16  show an embodiment wherein the head  300  is provided with grooves  304 G in the slots  304  for receiving torsion type springs T/S of the type illustrated in FIG.  16 . With this type of arrangement, the springs T/S can be disposed in position and the arms (not shown) slid into the slots and pinned in position. 
     FIGS. 17 to  19  show a variation in locking arrangement. In this instance the locking element takes the form of a disc  410  which is, as best seen in FIG. 18, slotted or recessed at four locations  410 A (one for each of the arms), while the arms which cooperate with this type of locking arrangement have, as shown in FIG. 20, an open locking slot  402 C. When the arms or blades are deployed, such as by inversion or the use of springs, disc  410  is rotated through the use of key-like arrangement  410 K shown in FIG. 17, so that the arcuate sections  41 OB of the disc  410  defined between the slots  410 A, enter the open locking slots  402 C of the arms. Once in this condition, the closing movement of the arms is resisted. 
     As mentioned above, in some instances, it is advantageous to be able to project the hooks toward their targets using devices such as grenade launchers. However, prior to being fired toward their target, it is preferred to be able to maintain the arms in their folded or storage positions. Further, it is preferable that the arms open up during their flight and switch from inoperative to operative positions. 
     FIG. 21 shows an embodiment which is adapted to meet these requirements. In this embodiment, the arms  502  are biased out by a flat star-shaped spring arrangement  550 , while the arms  502  are provided with hooks or clasp-like holders  502 G which grip the inner periphery of a barrel BA of a launching device (not shown) such as an M203 grenade launcher. These hooks  502 G can be riveted (welded etc.,) to the arms or can be formed by suitably shaping the blade per se. 
     As will be appreciated, immediately after being fired into the air, the arms  502  will swing out toward their respective operative positions under the bias of the spring  550  and will remain essentially in these positions even upon reaching the target. 
     It is worth noting that, in accordance with the present invention, even if one or more of the arms only assume a half-open state, that the function of the grappling hook will be impaired and that the arms or blades can dig into a surface or surfaces in a manner which will adequately bear the required load. The possibility that the arms will pull completely open is also high. 
     The arrangement in FIG. 21 is illustrated as having a rigid shaft  512  which is threaded into the head member  500 . While this arrangement does not have a locking arrangement pre se, one could be provided by flattening off the top of the head and retaining locking device such as illustrated in FIG. 3 or  5 , in position using a bolt and washer arrangement. In order to facilitate manufacture of the arms, the openings which receive the pawls of the locking device can be simply drilled or cut so as to take the form of a slot  502 C which is open at the top edge of the arm in the manner indicated in broken line. 
     FIG. 22 shows an arrangement which can be used in place of the hooks shown in FIG.  21 . In this embodiment, a semi-rigid elastomeric sleeve  660  is slipped over the barrel BA of the launching device and used to temporarily retain the arms of the hook in a folded or stored state. As shown, the tips of the arms (shown in phantom) seat in a recess  662  which extends about the whole sleeve thus defining a shallow toroidal space. It will be noted that for the simplicity of illustration, the shaft and other elements of the grappling hook are omitted. 
     FIGS. 23 and 24 show a further embodiment of the invention. This arrangement is adapted to support three blades. As will be appreciated from FIG. 23, the head  700  is formed of round stock and the recesses  704 , which are arranged to receive the blades are, in this instance, arranged at equidistant 120° spacings. 
     FIG. 24 is a sectional view at taken along section line XXIV—XXIV of FIG. 23, and shows details of how the shaft  712  is connected to the head portion of the device. In this embodiment, in order to receive an enlarged upper end portion  712 A of the shaft, the head  700  is formed with a blind bore  700 A having a diameter very slightly in excess of the OD of the enlarged upper portion  712 A. A set of coaxial bores  700 B,  712 B are formed radially through both the lower end of the head  700  and through an upper end of the upper end portion  712 A of the shaft. These bores are sized to receive a bolt  714  and a sleeve nut  716  which, as will be appreciated, is received in a radial bore on one side of the blind bore  700 A and arranged to threadedly engage the threaded end of the bolt  714 . 
     This particular type nut and bolt arrangement is suitable in the case wherein the head is formed of aluminum alloy or the like type light metal alloy and forming threads directly in the metal is not practical. However, in the event that the head  700  is formed of a steel or the like, then it is within the scope of the invention to directly tap one end of the radial bore  700 B and to use a commercially available bolt. 
     The locking arrangement  706  which is located at the top of the head can take any of the forms shown in FIGS. 3 and 4, for example, and is secured in place using a screw  707  which is received in a tapped blind bore  708 . The shaft  718 , in this embodiment, can be solid or can be formed of a braided aircraft cable with the metal end portions (viz., the enlarged upper end  712 A and a ring  720 ) securely mated thereto. 
     The blades which are used with this and/or any other embodiment, can be shaped in the manner depicted in FIG.  25 . This blade  800  has a more acutely angled end or tip  802  so as to provide an even greater grip on hard surfaces such as concrete, steel, and the like type of materials which are apt to be encountered when scaling a building. The degree by which the curvature of this blade is increased as compared to the previously disclosed ones is evident from the phantom line outline  803 . 
     FIG. 26 shows yet another blade design. In this arrangement the blade or arm  800  is provided with a steel or aluminum ball  804  at the end. This blade or arm  800  is designed for use on softer surfaces wherein the ball  804  is provided to prevent the tip of the blade from digging excessively into a soft surface such as soil or the like. 
     FIG. 27 is a side elevational view of a further embodiment of the invention. In this arrangement, flat springs  901  are provided to permit the blades  902  to be biased to an open or operative position and selectively locked in the operative position. In this arrangement, the springs  901  each have their lower ends secured to the side of the head by way of screws or the like type fasteners  904 . The springs  901  are sufficiently flexible to permit themselves to be folded over when the associated blade is folded down into a non-operative position such as depicted by the blade on the left handside of this figure. Means for retaining the blades  902  in the folded position are advantageous in this instance. Such an arrangement is similar to the retaining structures which are illustrated in FIGS. 21 and 22, merely by way of example. However, as will be apparent hereinafter, the retaining structures are not limited to such arrangements. 
     When the blades  902  are released and rendered free to rotate out to operative positions under the influence of the bias of springs  901 , the free ends of the springs  901  are able to, upon the respective blade reaching its operative fully extended position, engage in shaped recesses  906  which are cut into the lower edges of the blades  902 . As will be appreciated, in this state each blade  902  is prevented from returning to a folded or non-operative position both by the bias which is produced by a spring  901  and by the abutment of the free end of the spring against an engaging surface of the recess  906 . 
     When it is desired to stow the device, all that is necessary is for the user to press the spring  901  with a thumb or finger and to fold each spring  901  over and induce the free end to move out of the recess  906  in which it is engaged. The blades  902  can then be folded down against the side of the head  908  thus inducing the situation shown on the left of the drawing. 
     As mentioned previously, the invention can take the form of a three-blade arrangement. FIGS. 28A,  31  and  32  show arrangements of an embodiment which utilizes such a three-blade form. The arrangement which is shown in FIG. 28A is such as to use socket head cap screws  950  (see FIG. 28B) as the pins which connect the blades  951  to the head  952  of the device. As will be appreciated from the partially sectioned view of FIG. 28A, the three blade head arrangement is such as to provide sufficient space for easy access to the screws  950  which are used to pivotally support the blades  951  and thus facilitate easy interchange of blades should one become broken or if a different type of blade is required for a particular operation. 
     FIGS. 29 and 30 show examples of spring loaded bolts/pins which can be used in connection with the embodiments of the invention shown in FIGS. 31 and 32. 
     In the embodiments shown in FIGS. 31 and 32, the “three blade” head (as it will be referred to)  1000  is formed with a third bore  1001  which is located above those ( 1002 ) in which the support pins (e.g. the socket head cap screws)  1004  are disposed. Depending on the pin which is selected for use, these third bores  1001  can be either tapped or plain. A tapped bore however, permits the use of both of the arrangements shown in FIGS. 29 and 30. 
     More specifically, the arrangement shown in FIG. 29 is a hand retractable spring plunger  1006  which has a tapped body  1008  and spring loaded pin  1010  reciprocally received therein. The head  1000  shown in FIG. 32, which is usually knurled for a good grip, is connected with the pin  1010  so that it can 5 be manually retracted against a spring bias from a protruding position. These type of devices are commercially available and are marketed by various manufacturers. 
     As best seen in FIG. 32, the plungers  1006  are threaded into the third bores  1001  on the opposite side of the blade support structures as the cap screws  1004  (which are received in tapped bores  1002 ) to maximize the amount of space available for an operator to grasp a head  1000  and to retract the pin  1010  with the minimum of interference from the remaining components. The bores  1001  are located so as to correspond with the upper end portions of the arcuate slots  1016  which are formed in the blades  1018 . This enables the pin  1010  to projected into the slot  1016  when the blade  1018  is pivoted to an operative position and to lock it in place. 
     Manual retraction of each of the pins  1010  from the arcuate slots  1016  permits the corresponding blade to be pivoted back to its stored or folded position. Release of the head  1000  enables the pin  1010  to again project. However, this time the pin  1010  can extend adjacent an inboard edge of the blade  1018  and thus block pivotal motion away from the stored state. Accordingly, to unfold the device, each blade  1018  must be released via retraction of a pin  1010 , the blade  1018  pivoted toward an operative position and the pin  1010  released so as to protrude into the slot  1016  formed in that blade. 
     In addition to the sturdy and simple arrangement the above structure represents, the provision of the plungers  1006  actually provides each blade  1018  with a third point of support when they are deployed, which increases the strength of the head-blade interconnection. This of course is such as to improve the strength of the body-blade connection. 
     A combination of spring and plunger arrangement can envisaged. The spring, in this instance, can any one of those depicted in FIGS. 16,  21  or in  27 , merely by way of example, That is to say, the operator only needs to retract a plunger and allow the spring arrangement to pivot the blade to an operative position. With three simple operations the device can be readied for use. When it is desired to stow the device, each plunger can be retracted and the blade manually pressed down against the spring force. When the plunger is released, it engages an edge of the blade and prevents it from being pivoted back out to its operative state. Thus, three simple operations can ready the device for stowage. 
     The pin/bolt arrangement  1050  which is shown in FIG. 30, is a double ball ring-grip self locking pin. The two balls  1052  at the end of the pin  1050  are spring biased and once inserted into a bore tend to remain in position until such time as sufficient tractive force is applied to the ring. These types of locking arrangement can be simply inserted and removed from the third bores  1001  as desired. 
     Although the present invention has been described with reference to only a limited number of embodiments, the various modifications and changes which can be made without departing from the scope of the invention, is limited only by the appended claims, and will, in light of the preceding disclosure, be self-evident to the person of skill in the art to which the present invention pertains. By way of example, even though the embodiments have been illustrated as having a total of three or four blades, the invention is not so limited and the device may have as many blades as is deemed appropriate. For example, the device may be equipped with 4 or 8 pairs of blades (viz., 8 or 16 blades) or can have an odd number of blades. Additionally, a mixture of different sized/shaped interchangeable blades may also be employed to maximize the gripping effect on different closely juxtaposed surfaces such as concrete and steel.