BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The invention is directed to the field of grounding where it is desired to securely ground one surface with respect to another and wherein relative motion may take place between such surfaces. This may occur, for example, where a ground cable is clamped to a vehicle while the same is being fueled and where by inadvertence, or mistake, the vehicle is moved prior to release of the clamp. Additionally, the clamp may be used for welding where it is desired to provide a ground path for the welding apparatus and the rapid movement of the welding equipment away from the area of the clamp could cause injury to the operator or to the object being welded if removal of the clamp is forgotten.
2. DESCRIPTION OF THE PRIOR ART
According to certain prior art references, clamps were available which could be operated remotely by means of a cable to cause them to be opened. One such clamp is found in U.S. Pat. No. 3,470,523, to Milo, issued Sept. 30, 1969. This clamp is of the general alligator type having two handles, each terminating in a contact jaw and having a spring therebetween to cause the jaws to be held in close contact with an object placed therebetween. A cable is attached to a first of the handle ends and brought about a roller attached to the end of the second handle. Sufficient forces exerted on the cable cause the handles to be moved towards one another against the influence of the spring thereby releasing the grip of the jaws on any object placed between the contacts. The action, however, would not be a quick, positive release, but one merely sufficient to permit the movement of the clamp with respect to the surface. Should a current be flowing in the ground cable at this time, severe arcing and sparking would take place all along the travel of the clamp along the surface. It is not possible with a clamp of this type to get an instantaneous, quick release by freeing the clamp from further contact with the surface and eliminating the contact between the clamp and the surface which resists the further removal of the clamp from the surface. The patent to Trachtenberg, U.S. Pat. No. 3,183,469, issued May 11, 1965, presents a very similar type of clamp suffering from the same type of release problem discussed above with respect to the Milo patent.
SUMMARY OF THE INVENTION
The present invention overcomes the difficulties noted above with respect to prior art devices by providing a grounding clamp which can be quickly and easily released in a positive, definite manner as soon as it is desired to release the same, or should there be accidental movement between the surface to be grounded and the clamp. Forces exerted upon the cable connecting the clamp to the equipment to be grounded causes the release of the clamp in a rapid, positive manner. This is provided by means of a clamp fabricated from an over-center type of locking wrench whereby sufficient contact forces can be exerted by the jaws of such wrench to a surface to be contacted to provide a good electrical connection therewith. Connected to the wrench is a conductive cable used to provide the ground path between the clamp mechanism and the equipment to be grounded. Coupled between the conductive cable and the release lever of the over-center type wrench are various operating mechanisms which make use of the forces exerted upon the conductive cable due to the relative movement of the grounding surface, or forces exerted directly upon the conductive cable to cause the rapid, positive release of the wrench mechanism from the grounding surface. In a first embodiment, the operating mechanism consists of an operating link connected between the releasing lever and the conductive cable. By means of suitable guides and attaching devices the position of the conductive cable is restricted so as to be in contact with the upper portion of the operating link such that when a force, of the required level is applied, the conductive cable displaces the operating link which in turn operates the release lever to cause the jaws of the clamp to open in a rapid, positive manner. In other embodiments, a roller is attached to the normal release lever of the over-center type locking wrench and the conductive cable caused to traverse such rollers in such a manner that the relative movement of the surface to forces applied to the conductive cable will cause the roller to displace the release lever and release the wrench mechanism. In another embodiment, the conductive cable has a trigger ring installed thereabout to operate the release lever when the conductive cable has been displaced a sufficient distance to cause the trigger ring to bear upon the ring of the release lever and operate same. Additionally, an extra cable, or wire rope, may be attached to the conductive cable, which wire rope may be applied selectively to the release lever so that the release feature may be selectively employed. Finally, a roller may be attached to one of the handles of the clamp and the end of the conductive cable coupled directly to the release lever through an appropriate lug or coupling such that when the permitted forces in the cable are exceeded the clamp will rapidly open and release. It is therefore an object of this invention to provide an improved form of remotely released grounding clamp.
It is yet another object of this invention to provide a grounding clamp which will open in a positive, rapid manner when forces are applied to the cable attached thereto or when the surface to which it is clamped is caused to move with respect to the cable.
It is still another object of this invention to provide an improved grounding clamp wherein the cable employed for grounding is used to actuate the release lever of the clamp.
It is yet another object of this invention to employ the grounding cable to operate, through intermediate members, the release lever of an over-center locking clamp when forces applied to the cable exceed a predetermined amount, to cause the rapid release of the clamp from the surface to which it is applied.
Other objects and features of the invention will be pointed out in the following description and claims, and illustrated in the accompanying drawings, which disclose, by way of example, the principles of the invention and the best modes which have been contemplated for carrying them out.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings in which similar elements are given similar reference characters.
FIG. 1 is a side elevational view of an overcenter locking wrench constructed in accordance with the prior art teachings and which appears as FIG. 1 of U.S. Pat. No. 2,519,130, issued July 4, 1950.
FIG. 2 is a side elevational view of a clamp constructed in accordance with the concepts of the invention.
FIG. 3 is a front elevational view, foreshortened, of the operating linkage of FIG. 2.
FIG. 4 is a front elevational view, taken along the lines 4--4 of FIG. 2.
FIG. 5 is a fragmentary side elevational view of yet another form of the clamp constructed in accordance with the concepts of the invention.
FIG. 6 is a front elevational view taken along the lines 6--6 of FIG. 5.
FIG. 7 is a fragmentary side elevational view of yet another form of clamp constructed in accordance with the concepts of the invention.
FIG. 8 is a side elevational view of another form of clamp constructed in accordance with the concepts of the invention.
FIG. 9 is a side elevational view of still another form of clamp constructed in accordance with the concepts of the invention.
FIG. 10 is a side elevational view of yet another form of clamp constructed in accordance with the concepts of the invention.
FIG. 11 is a side elevational view of an additional form of clamp constructed in accordance with the concepts of the invention.
FIG. 12 is a fragmentary side elevational view of a further form of clamp constructed in accordance with the concepts of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIG. 1 there is shown an over-center locking wrench as found in FIG. 1 of U.S. Pat. No. 2,514,130 issued July 4, 1950, entitled "Locking Wrench and Pliers" representative of the basic over-center locking mechanism shown in the present device. The operation, as described in this patent, is summarized as follows: The toggle linkage formed between the lower handle 5 and the locking link 11 are pivoted together at point 12. The opposite end of the locking link 11 is pivoted as at 16 and handle 5 is pivoted to the lower jaw 2 at a pin 6. In order to lock the locking wrench to an object X placed between the upper jaw 1 and lower jaw 2, the handle 5 is moved towards handle 4 such that the pivot 12 is placed in the position over the center line drawn through the pivot 6 and the pivot 16. In this condition, a stable locking over-center position is established which will remain that way causing the wrench to hold tightly to the object X placed between the jaws 1 and 2. When it is desired to release the grip upon the object X, the release handle, or lever 25, is moved away from the handle 5 in order to allow the locking link 11 to move such that the pivot 12 is below the center line through the pivots 6 and 16 creating a non-stable over-center position which allows the tension spring 8 to pull the lower jaw 2 rapidly away from the upper jaw 1 causing a quick disengagement of the wrench from the object X placed between the jaws 1 and 2. Based upon the strength of the spring 8, a snap action release is provided. By the proper selection of the dimensions, and its placement, the release lever 25 may be arranged to operate when moved towards or away from the handle 5 or provision may be made to permit release lever 25 to be operated in either direction. In other arrangements, it is possible to place the release lever in other positions along the tool, but in any case it is necessary merely for the release lever to be able to move the pivot pin 12 from its over-center stable position to its overcenter unstable position to cause unlocking of the wrench in a rapid manner.
Turning now to FIGS. 2, 3 and 4, there is shown a clamp 102 constructed in accordance with the concepts of the invention. Clamp 102 has a first handle 104 to which is fixidly attached a first jaw member 106 preferable coupled as at 108. Coupled to the first jaw member 106 by pivot 108 is a second jaw member 110. Coupled thereto by pivot 112 is a second handle 114 having a locking link 116 coupled thereto as by pivot 118 and extending to the first handle 104 in the method fully described in the above cited prior art patent. Releasing lever 120 is pivotly connected to the second handle 114 as at 122 and has placed thereupon an extension 124 which is better seen in FIG. 3. Extension 124 has two apertures 126 therein to receive therethrough the legs 128 of operating link 130. The operating link 130 sits astride the second handle 114 and the first handle 104, as is generally shown in FIG. 3. Fasteners 132, in conjunction with annular rings 134 on each of the legs 128 of the operating link 130 fasten the operating link 130 to the extension 124 of the release lever 120 and also establishes the position of operating link 130 with respect to the release lever 120. Bearing surface 136 atop the operating link 130 will receive, in a manner to be disclosed below, the conductive cable 138 for operating the clamp 102 and for providing the grounding path, as was described above. The conductive cable 138 from the object to be grounded (not shown) extends through the ring 142 of guide 140. The outer shell of the ring 142 is metal but the inside is protected by a plastic or rubber insert. The guide 140 is supported and anchored in place by a fastener 146 passed through a suitable aperture in extension 144 and attached to the first handle 104. The conductive cable 138 passes through the ring 142 of the guide 140, over the bearing surface 136 of the operating link 130 and thence to a coupling 150 attached to the first jaw member 106 of the clamp 102. Coupling 150, better shown in FIG. 4, has a first generally U-shaped member 152 attached to the first jaw member 106 as by fastener 154 and having a second complimentary plate 156 moved with respect to the inturned portion of the member 152 by means of a second fastener 158. The end of the conductive cable 138 being placed between the inturned portion of member 152 and plate 156 and captured therebetween by the tightening of the fastener 158.
Clamp 102 will be applied to a surface to provide the necessary ground path for the equipment attached at the other end of the conductive cable 138. Using the clamp 102 in its normal manner, that is, after the necessary adjustments have been made of the clamp 102 for the thickness of the surface to which it is to be attached, the handle 114 will be brought towards the handle 104 to cause the locking of the clamp 102. In this manner, because of the adjustable force which may be applied by the clamp 102, a positive ground connection is made between the cable 138 and the grounding surface to which the clamp 102 is attached. Such a grounding is required for vehicles which are being fueled and which, in order to minimize the possibility of explosion, requires a ground path for any charges built up upon the vehicle during such refueling. Upon the completion of fueling it is desirable to be able to release the clamp 102 remotely or in the case where the vehicle is accidentally moved prior to the time that the clamp 102 is disconnected it is essential that the clamp 102 be quickly released. The clamp 102 may be made to operate either by a tug upon the grounding conductive cable 138 itself, or by movement of the surface to which the clamp 102 is attached.
More specifically, the release of clamp 102 is achieved in the following manner: assume, for example, a force is being exerted upon the conductive cable 138 from the direction to the left of FIG. 2, the conductive cable 138 as it passes over the bearing surface 136 of the operating link 130 will cause the link 130 to move downwardly until the annular rings 134 on the legs 128 of the ring 130 engage the extension 124 of the release lever 120 causing the release lever 120 to move in a clockwise direction about the pivot 122 and allow locking link 116 to move to its nonstable over-center position and permit the tension spring (not shown) to rapidly open the lower jaw member 110 thereby releasing the clamp 102 from the surface to which it is attached. Generally, movement of the surface to which the clamp 102 is attached, for example, to the right of FIG. 2 will cause the conductive cable 138 to be stretched and tightened in the area of the bearing surface 136 of the operating link 130 causing the operating link 130 to cause release of the clamp 102 in the manner set forth above.
With the clamp 102 of FIG. 2 in order to secure the cable 138 to the clamp 102 it is necessary to add a coupling such as coupling 150 thereto, however, alternative arrangements are possible, for example, the first jaw member 160 (shown in FIGS. 5 and 6) is fabricated in such a manner as to provide an extension 162, as seen in FIG. 6, which can receive conductive cable 138 in a recess 164 formed therein. A clamping plate 166 will be secured thereto and a fastener 168 will be used to fasten the conductive cable 138 securely within the recess 164 of the extension 162 of the first jaw member 160. A further form of combined guide and coupling device for the conductive cable 138 is shown in FIG. 7. In the clamp 170, a unitary structure 172 has at a first end a ring 174 serving as the guide for the conductive cable 138 and at a second end a clamp 176 for receiving and coupling conductive cable 138 to the clamp 170. A fastener 178 extends through the clamp end 176 which is formed as a folded over ring in order to trap and hold the end of the conductive cable 138 therein. Thus, as is shown in FIGS. 2 through 7 various forms of coupling devices may be employed to couple the conductive cable 138 to the clamp member itself. This may be provided by accessory items added to the clamp individually, as is shown in FIG. 2, or by forming a jaw member itself in such a manner that it is a portion of the clamping device, as is shown in FIG. 5, or by providing a single, unitary device including both the clamping device and the guide means as is shown in FIG. 7. The guide, as shown in FIG. 2, may also be a separate member separately attached to the clamp.
Turning now to FIG. 8 there is shown a clamp 200 employing a different approach to the release mechanism. The basic over-center locking wrench is again shown in FIG. 8, however, the lower jaw member 202 is provided with a coupling member 204 in a manner similar to that described with reference to FIG. 5 for receipt therein of the end of the conductive cable 138. The release lever 206 normally found within the second handle 114 or just outside thereof has been moved to a position closer to the first handle 104 as is shown by the release lever 206 of FIG. 8. The release lever 206 is coupled as by pivot 208 to the second handle 114 and has attached intermediate its ends a roller 210. Attached to the first handle 104 is a cable guide 212 generally in the form of a ring adjacent the remote end of the handle 104, remote from the first jaw member 106. The path of the conductive cable 138 extends from the coupling member 204 on the second jaw member 202 over the roller 210 through the cable guide 212 to the object to be grounded. When forces are exerted upon the cable 138 to the right of FIG. 8 this causes the conductive cable 138 to tighten against the roller 210 and displace it downwardly moving the release lever 206 about the pivot 208 in a clockwise direction and cause release of the jaw members 106 and 202, as was described above. Similarly, the movement of the object placed between the jaw members 106 and 202, to the left of FIG. 8, will cause the shortening of the loop of the conductive cable 138 about the roller 210 and cause it to be operated in a manner just described.
Turning now to FIGS. 9 and 10 a slightly different approach is shown in the release of the clamps 220 and 230 respectively. In FIG. 9, the cable 138 is caused to pass through a guide 212 and thence through the loop 226 placed at the end of the trigger lever 222 pivotally mounted by pin 224 to the second handle 114. A trigger ring 228 is placed about the conductive cable 138 just ahead of the ring portion 226 of the trigger lever 222. An additional guide 213 is coupled to the upper handle 10 to guide the path of the conductive cable 138 between the trigger lever 222 and the coupling 162 of the upper jaw 160. When forces are applied to the conductive cable 138 causing the same to move to the right of FIG. 9 the conductive cable 138 will move to the right until the trigger ring 228 is brought into contact with the loop portion 226 of the trigger lever 222 and causes the same to be moved to the right of FIG. 9, or in a clockwise manner about the pivot 224 causing the rapid release of the locking clamp 220 and the release of the object placed between the jaw members 160 and 110. In FIG. 10 the clamp 230 is provided with an upper guide 238 to guide the conductive cable 138 in its path through the loop 234 of the trigger lever 232 to the coupling 162 of the upper jaw member 160. A trigger ring 236 is placed about the conductive cable 138 between the coupling 162 and the loop 234 of the release lever 232. Again, when forces are applied to the conductive cable 138 in a direction to the right of FIG. 10 the conductive cable 138 is moved to the right until the trigger ring 236 is brought into contact with the loop 234 of the trigger lever 232 causing same to be operated. In a similar fashion, should the surface to which the clamps 220 of FIG. 9, or 230 of FIG. 10 are attached, be moved to the left of the respective figures the same operation will occur causing the release of the respective clamps 220 and 230.
Turning now to FIG. 11 there is shown another form of clamp 250 which is operated by means of an additional wire rope 252 coupled to and carried along with the conductive cable 138. The wire rope 252 is attached to the conductive cable 138 as by the ring 253, or other suitable means, such that any force exerted upon the conductive cable 138 will similarly be exerted upon the wire rope 252. Conductive cable 138 passes through the guides 212 and 213 and is anchored to the clamp 204 on the lower jaw member 202 in a manner as was described with reference to FIG. 8. Release lever 254 has a recess 256 to which the end of the wire rope 252 may be selectively coupled. In this manner, with the wire rope 252 coupled within the recess 256 of the release lever 254 any movement of the conductive cable 138 to the right of FIG. 11 will cause the release lever 254 to be operated such as to release the object held between the upper jaw member 106 and the lower jaw member 202 of the clamp 250. Should it be desired to remove the release feature, but yet retain the connection for the conductive cable 138 to provide the necessary ground path, it is only necessary to remove the wire rope 252 from the recess 256 of the release lever 254. Thus, the grounding function is continued while the release feature is removed. A lug, clamp or other coupling may be employed to couple the wire rope 252 to the release lever 254.
In FIG. 12 there is shown another form of releasable clamp 260. In the device of FIG. 12 the end of the conductive cable 138 is connected to a lug 268 attached adjacent the remote end of the release lever 120 then passes over a roller 264 attached to the second handle 114' by means of a support 262 and then through a guide 266 attached adjacent to the remote end of the second handle 114. Thus, any forces applied, in the direction to the left of FIG. 12, upon the conductive cable 138 will cause clockwise movement of the release lever 120 about the pivot 122 causing the releasing of the locking action of the clamp 260.
While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiments, it will be understood that various omissions and substitutions and changes of the form and details of the devices illustrated and in their operation may be made by those skilled in the art, without departing from the spirit of the invention.