US3641473A

US3641473A - Vehicle-grounding clamp

Info

Publication number: US3641473A
Application number: US41249A
Authority: US
Inventors: Thomas J Attaway
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-05-28
Filing date: 1970-05-28
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08

Abstract

A grounding clamp is constructed of two arms pivotally interconnected intermediate the ends thereof with each arm having a handle end and a jaw end. The jaw ends of the arms are spring biased toward one another. The arms of the clamp are formed of a synthetic plastic having high electrical insulating characteristics. Replaceable metal jaw elements are secured to the jaw ends of the arms and the jaw elements include perpendicularly projecting spiked teeth. The teeth of each jaw element project toward the opposite jaw element, and the tips of the teeth of each jaw element lie in substantially parallel planes. An electrical lead extends to each jaw element with one of the leads grounded and the other lead in series circuit with a signal triggering device. When the clamp engages a portion of the vehicle to be grounded between the teeth, the vehicle is grounded and the triggering circuit completed through the vehicle. In an alternate embodiment, the teeth are formed by the pointed ends of mounting bolts which extend from the jaw ends of the arms through the jaw elements. A snap apart electrical connector is provided in an electrical lead cable which extends between an electrostatic drain and the clamp and the connector will open to prevent damage of the grounding clamp if the vehicle is moved without first removing the clamp.

Description

United States pateiet Attaway [451 Feb. 8, 1972 [54] VEHICLE-GROUNDING CLAMP [72] Inventor: Thomas J. Attaway, 50 SE. 14th St.,

Dania, Fla. 33304 22 Filed: May 28,1910

211 Appl.No.: 41,249

[52] US. Cl. ....339/14 R, 339/255 P [5 1] Int. Cl ..H0llr 11/22 [58] fieldofsearch ..339/14,255,260,59,28, 29;

2,522,810 9/1950 Bailey... ..339/200 3,470,523 9/1969 Milo ..339/45 1,910,022 5/1933 Legg 339/259 x 2,375,656 5/1945 Jackson ..339/255 P x 119 25 957 2/1966 Caldwell ..317/2 R Primary Examiner-Marvin A. Champion Assistant ExaminerRobert A. Hafer Attomey-Polachek & Saulsbury [57] ABSTRACT A grounding clamp is constructed of two arms pivotally interconnected intermediate the ends thereof with each arm having a handle end and a jaw end. The jaw ends of the arms are spring biased toward one another. The arms of the clamp are formed of a synthetic plastic having high electrical insulating characteristics. Replaceable metal jaw elements are secured to the jaw ends of the arms and the jaw elements include perpendicularly projecting spiked teeth. The teeth of each jaw element project toward the opposite jaw element, and the tips of the teeth of each jaw element lie in substantially parallel planes. An electrical lead extends to each jaw element with one of the leads grounded and the other lead in series circuit with a signal triggering device. When the clamp engages a portion of the vehicle to be grounded between the teeth, the vehicle is grounded and the triggering circuit completed through the vehicle. In an alternate embodiment, the teeth are formed by the pointed ends of mounting bolts which extend from the jaw ends of the arms through the jaw elements. A snap apart electrical connector is provided in an electrical lead cable which extends between an electrostatic drain and the clamp 7 Claims, 10 Drawing Figures PATENTEWEB 81972 3.641.473

1 LIIK 1 INVENTOR THOMAS J. ATTAWAY BY W37? ATTORNEYS mmrm am SHEET 2 OF 2 INVENTOR THOMAS J. ATTAWAY ATTORNEYS An electrical clamp having a separate contact terminal in each jaw thereof.

During the loading and unloading of tank vehicles containing flammable fluids, there is a great fire and explosion hazard which is, to some extent, reduced by the provision of an electrical ground connected to the vehicle. The electrical ground serves to discharge any electrostatic charge which is carried by the tank vehicle. If the electrostatic charge is not dissipated prior to the loading and unloading procedure, a discharge spark which might occur during the procedure could result in an explosion. The vehicle ground should be maintained during the vehicle loading and unloading operation because an electrostatic charge can also be accumulated by the movement of the flammable fluids in the tank. Thus, any charges must be continuously drained to a ground.

Several electrostatic drain devices have been developed to insure that the tank vehicle is continuously grounded during the loading or unloading operation. Most of these devices include not only a visible or audible ground signal indicator but a switching mechanism which controls the operation of the pumping facilities so that the vehicle cannot be loaded or unloaded if a proper ground is not maintained. Generally the electrostatic drain devices include a triggering circuit to activate the ground signal indicator along with any auxiliary switching means to control the fluid pumping operations. The triggering circuit includes a grounded terminal and the circuit is completed when a second terminal is additionally grounded. A clamp serves to complete a series electrical circuit between the grounded terminal and the second terminal through two leads of a ground cable. Each lead of the ground cable is electrically connected to one jaw of a ground clamp. Thus, the triggering circuit is completed only when the tank vehicle is grounded through the ground clamp with the vehicle shunting between the two circuit terminals.

Present ground clamps are constructed of electrically conducting metal arms which are pivotally interconnected. Because the ground clamp jaws each include terminals which must necessarily be insulated from one another and the metal arms, the jaws of the present ground clamps are mounted to the arms on insulated mounting pads with the securing means, e.g., bolts extending between the arms and the jaws,- further insulated with bushings. Due to the necessity of the insulating mounting pads along with the insulating bushings to assure that the jaw terminals will not short through the metal body of the clamp, the cost of the present clamps are high. Furthermore, replacement labor costs for the individual jaw members are high because of the pad and bushing assembly process. Unfortunately, the jaw members often break. Breakage of the jaw members is due to the fact that the tank vehicle often includes rusted or painted surfaces which must be penetrated by the jaw member to adequately ground the vehicle. Thus, the jaw member teeth are subjected to stresses, and breakage of individual teeth is common.

It is an object of the premnt invention to provide a vehiclegrounding clamp which is so constructed that it is not subject to any of the foregoing disadvantages.

More specifically, it is an object of the present invention to provide a vehicle-grounding clamp which greatly reduces the explosion hazard inherent with the loading of flammable fluids in a tank vehicle, is easy to use, durable and sturdy in construction, yet can be fabricated by mass production techniques at a cost appreciably lower than vehicle grounding clamps presently used.

Another object of the present invention is to provide a vehiole-grounding clamp which is constructed of a body formed of a synthetic plastic and having replaceable metallic jaw elements which are electrically isolated from one another.

A still further object of the present invention is to provide a vehicle-grounding clamp which includes an electrically insulating body and replaceable metallic jaw elements each of which includes a plurality of projecting teeth to engage portions of the vehicle to be grounded.

Yet another object of the present invention is to provide a vehicle-grounding clamp which includes means to adjust the height of clamp jaw teeth so that the tips of the teeth of opposed jaws lie in substantially parallel planes to assure maximum electrical contact between the jaw teeth and the vehicle to be grounded.

Another object of the present invention is to provide a vehicle-grounding clamp which includes an electrically insulating body and replaceable jaw elements with the jaw elements including teeth which are formed by mounting bolts which hold the jaw plate to the body.

A still further object of the present invention is to provide a vehicle-grounding clamp wherein the teeth of opposed jaws are formed by the tips of mounting bolts which secure an electrical contact plate to the clamp.

Other objects of the invention in part will be obvious and in part will be pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements and arrangements of parts which will be exemplified in the vehicle grounding clamp hereinafter described and the scope of which will be indicated in the appended claims.

In the accompanying drawings, in which are shown the preferred embodiments of the invention,

FIG. 1 is a perspective view of -a vehicle-grounding clamp and showing the clamp engaging a relatively flat metal portion of tank vehicle during a tank-loading operation.

FIG. 2 is a side view of the vehicle-grounding clamp and showing jaw teeth engaging a flat metal portion of the vehicle to be grounded; also shown is a snap apart electrical connector which is included in a twin lead electric cable running from an electrostatic drain device to the clamp.

FIG. 3 is a top plan view of the clamp illustrated in FIG. 2.

FIG. 4 is a sectional view taken substantially along the line 4-4 of FIG. 2 and showing a cylindrical metal sleeve which is bent to engage the twin lead cable running and thus prevent the cable from being pulled from the clamp.

FIG. 5 is a sectional view through the clamp the same being taken substantially along the line 5-5 of FIG. 2 and showing a pin which pivotally interconnects arms which form the clamp, along with a helical coil spring concentrically positioned about the pin and biasing the arms of the clamp so that the clamp jaws are urged together. 4

FIG. 6 is a sectional view through the jaw end of the clamp, the same being taken substantially along the line 66 of FIG. 2 and showing toothed jaw elements seated within the hollow channel shaped portion of the clamp and secured therein by mounting bolts; additionally shown are jaw teeth which project from each jaw element toward the opposite element along with positioning shims interposed between the jaw elements and the base of the channel shaped portion of the clamp.

FIG. 7 is a perspective view of the opposed jaw elements removed from the clamp and showing electrical leads extending to each jaw element.

FIG. 8 is a sectional view through an alternate embodiment of the clamp wherein the jaw elements are constructed of contact plates and spiked jaw teeth are formed by pointed tips of bolts which secure the contact plate to the jaw end of the clamp.

FIG. 9 is an enlarged sectional view through the snapapart connector element, the same being taken substantially along the line 99 of FIG. 2.

FIG. 10 is a view similar to FIG. 7 but showing a still further modified form of the invention.

The vehicle-grounding clamp of the present invention to be described hereinafter is designed for use in conjunction with an electrostatic drain apparatus generally of the type illus trated in US. Letters Pat. No. 3,343,154 and U.S. Letters Pat. No. Re. 25,957 along with other, electrostatic drains which include a vehicle ground signal indicator controlled by a triggering circuit in series with the vehicle to be grounded and an earth ground.

Referring now in detail to the drawings, the reference numeral denotes a vehicle-grounding clamp constructed in accordance with an embodying the invention. The grounding clamp 10 is formed of an upper and a

lower clamp arm

12, 14. Each arm l2, 14 is of substantially U-channel transverse cross section as illustrated in the sectional view of FIG. 5. The arms include

handle portions

16, 18 adjacent one end thereof and jaw portions N, 22 adjacent the opposite ends thereof. The arms 12,114 arepivotally interconnected by a pin 24 which extends through flanges projecting in opposite directions from each arm toward the opposite arm. The pin,-in fact, extends through openings in the opposed flanges, and it will be noted, that the flanges which project upwardly from the lower arm 14 are spaced apart a distance greater than the flanges which project from the upper. arm 12 and the flanges of the upper arm are nestably received between the lower arm flanges. The opposite ends of the pin 24 are suitably peened for captive retention. It will be observed that when the

handle portions

16, 18

of the arms are pivoted toward one another, the jaw portions 20, will separate from one another.

It is desirable to have the jaw portions biased toward one another and electrically engaging a metal portion of the tank vehicle. For this purpose a helical coiled spring 26 is concentrically mounted about the pin 24 with the

opposite end portions

28, 30 of the spring 26 extending tangentially of the helical coils toward the handle portions, 16, 18. The

spring end portions

28, 30 engage the hollow channel-shaped interior of the arms l2, 14. Thus, a counterclockwise torque (as viewed in FIG; 2) is applied by the spring 26 to the arm 12.

In order to increase the strength of the

arms

12, 14 in the region where the spring ends 28, 30 apply forces against the arms l2, 14, each arm is provided with a

rib

32, 34 which projects in opposite directions from the arms l2, 14 respectively. The reinforcing

ribs

32, 34 project from the bases of the proposed U-channel arms in opposite directions.

It should also be noted that the lower arm 14 includes a plurality, of spaced parallel transverse grooves which provide finger grips in the handle portion 18. Thus, the manipulation of the clamp is greatly facilitated and the user may quite readily grasp the handle portions with his fingers seated in the grooves and squeeze the handle portions together against the bias of the spring 26 to spread the jaws apart, whereby a metal portion of the tank vehicle, may be received between the jaws and electrical contact will be achieved between the vehicle and the electrostatic drain device.

Removable jaw members

38, 40 are seated within the U- channel interior of the

jaw portions

20, 22 of the clamp 10. The

jaw members

38, 40 include a substantially

rectangular baseplate

42, 44 and a plurality of spiked or pointed cylindrical protuberances 42 which project perpendicularly from the baseplate 44. Each of the protuberances 46 includes a pointed tip which serves to dig into a metallic surface of the vehicle to be grounded to assure an electrical contact. The

jaw members

38, 40 are preferably formed of molded one-piece construction. The width of the

baseplates

42, 44 is less than the distance between the sidewalls of the U-shaped channel interior of the

arms

12, 14 so that the jaw members may be inserted between the sidewalls of the arms and mounted therein with the longitudinal axis of the jaw members and the longitudinal axis of the arms lying in substantially coplanar relationship. In order to mount the

jaw members

38, 40, threaded openings 48 are provided through the

baseplates

42, 44 and matingly threaded bolts 50 extend through registered openings in the base of the U-channel arm to engage the threaded openings 48 It should be noted that the length of the spiked cylindrical protuberances 46 are uniform and that the

jaw portions

20, 22 of the arms l2, 14 do not move in parallel relationship to one another when the clamp is opened and closed. Ideally, the metal surface of the tank vehicle which is to be grounded includes two parallel flat surfaces and it is desirable therefore to maintain the tips of the protuberances 46 of the

jaw members

38, 40 in substantially parallel relationship so that they the desired parallel orientation of the tips of the

jaw members

38, 40. From an observation of FIG. 6 it will also be seen that the protuberances 46 projecting downwardly from the baseplate 42 are displaced from the protuberances 46 projecting upwardly from the baseplate 44. In fact, the embodiment shown includes six protuberances 46 extending upwardly from the baseplate 44, and three protuberances extending downwardly from the baseplate 42. It should also be noted that the protuberances projecting downwardly lie along the longitudinal axis of the baseplate 42, while the protuberances projecting upwardly from the baseplate 44 are grouped in pairs, each pair extending through a transverse plane perpendicular to the baseplate 44. The transverse plane substantially includes the corresponding protuberance projecting downwardly from the baseplate 42. Thus, the

jaw members

38, 40 include groups of three protuberances, i.e., two upwardly projecting and one downwardly projecting, with each group lying in a transverse vertical plane, and spaced from other groups of protuberances lying in similar transverse planes. This specific protuberance configuration permits three-point contact with each set (or group of three) protuberances extending in a single transverse plane. This three-point contact will facilitate the gripping of curved surfaces by the jaw members.

Attention is now directed to a twin lead cable 54 which extends into the arm 14 of the clamp 10. The cable 54 is sheathed in configuration. The cable extends into the hollow U-channel interior of the arm 14 and is captively retained by a sleeve member 56 (see FIG. 4). The sleeve member 56 is formed of a suitable bendable metal and tightly grips the cable 54. It should also be noted that the sleeve member 56 is in turn secured to the arm 14 by a rivet 58 or the sleeve member may be made integral with the arm 14 and form a tubing for the cable 54. The cable 54 includes two leads 60, 62 which extend and, are electrically interconnected to the

jaw members

38, 40 respectively. In order to make a secure electrical connection between the jaw members and their respective leads, each jaw member includes a flange 64 which projects from the

baseplates

42, 44 in a direction parallel to the protuberances 46, but is' of a length less than that of the protuberances 46. Each

lead

60, 62 extends through an opening in a flange 64 and is then bent upwardly and secured under the head of a bolt 66.

It should be noted that an important feature of this invention is the fact that the

jaw members

38, 40 are not electrically interconnected through the clamp 10 itself and the only electrical connection between the jaw members must be through a metal portion of the tank vehicle to be grounded. To insure that the

jaw members

38, 40 do not make inadvertent electrical contact except through the desired vehicle medium, this invention provides for an electrically insulating clamp body. For this purpose, the upper and lower arms l2, 14 are formed of a synthetic plastic which has a relatively high volume resistivity. Suitable synthetic plastics for use as the

arms

12, 14 are acrylonitrile-butadiene-styrene, polypropylene, linear polyethylene (high density) and polystyrene. As previously mentioned, these synthetic plastics are highly suitable for upper and lower arm fabrication, and may be easily injection molded. Additionally, their resistivity in ohms per cubic centimeter is relatively high (approximately 10"). Additionally, a suitable synthetic material for upper and lower arm fabrication is glass reinforced polyester resin which is molded, and has a volume resistivity in ohms per cubic centimeter of approximately 10'.

One should additionally note that in order to prevent electrical contact between the

jaw members

38, 40 when the clamp is idle and there is no metal portion to be grounded between the clamp jaws, a suitable idle position stop is provided. The stop is formed of rnatingly projecting

bosses

64, 66 which abut one another before the spiked tips of the protuberances 46 make contact with one another. Furthermore because the protuberances 46 of each baseplate42, 44 are spaced from one another, the tendency for the

jaw members

38, 40 to make electrical contact without an intervening metallic body is greatly reduced.

It should also be noted in passing that the jaw ends of the

arms

12, 14 include an upwardly projecting

flange

68, 70 which serves as a protective guard preventing damage to the bolt heads 50. This is because the

flanges

68, 70 project from the base of the arms l2, 14 a distance greater than the height of the bolt heads 50.

In order to prevent injury to the electrostatic grounding device and/or the clamp or cable 54 if the tank vehicle is inadvertently moved, without first disconnecting the grounding clamp 10, a pull apart electrical connector 72 is provided in the cable 54. The connector 72 includes two

snapapart sections

74, 76, each of which includes a longitudinal socket 78 which receives a mating cylindrical contact plate 80 which projects from the opposite section. If the vehicle is moved without first disconnecting the grounding clamp 10 the

section

74, 76 will separate, and the respective contact plates 80 will slide from the sockets 78. Thus, the vehicle will move with the grounding clamp 10 attached along with a portion of the cable 54 leading to and including the connector section 76.

An alternate embodiment of the invention is illustrated in the sectional view of FIG. 8. In this embodiment the upper and lower arms 12a and 140 include jaw members 38a and 400 which are of a difi'erent configuration. The jaw members 38a and 40a include rectangular baseplates 42a and 44a which are nestably received within the hollow U-channels of the jaw portions a, 22a of the arms. The baseplates 42a, 44a do not include one-piece unitarily formed protuberances, however, and in fact theprotuberances are formed by the bolts 500, which secure the baseplate 44a to'the base of the U-channel of the arm 14a. The baseplate 44a includes a plurality of threaded openings 48a which are positioned and distributed along the surface of the baseplate in the same pattern of the protuberances 46 of the preferred embodiment. The bolts 50a are of a length longer than the length of the previously used bolt 50 (in the preferred embodiment and include spiked or pointed tips. In order to maintain the tips of the bolts 50a in proper planar alignment and to insure that the tips of the bolts 50a of 'both jaw members lie in substantially parallel planes, each bolt is individually adjustable through the use of shim washers78. The baseplates 42a, 440 are secured to the

jaw portions

20, 22 of the arms by the bolts 50a which extend through openings in the jaw portions 20a, 2741 in registry with the threaded openings 48a of the baseplate.

As was previously mentioned, the distance which the tips of the bolts 50a extend past the baseplate is adjustable through the use of washer shims 78. Thus, in the application illustrated in FlG.'8 the bolt which is adjacent the boss 640 should extend a distance beyond the baseplate 444 which is greater than that of the other bolts. Therefore this bolt does not include a shim washer 78. The precise adjustment of the bolt is in fact determined by the specific vehicle application and therefore is not of critical importance. It should also be noted that the baseplates 42a, 440 are connected electrically to their

electrical leads

60, 62 through the use of the

bosses

64a and 66a in a manner identical to that of the preferred embodiment.

A further embodiment of the invention is illustrated in FIG. 10. In this embodiment, a clamp 10b is identical in construc' tion to the clamp 10 previously described except for a slight variation in the

jaw members

38b, 40b.

This embodiment employs an alternate structure for securing electrical connections between the

jaw members

38b, 40b and their respective leads b, 62b. Each jaw member includes a bore 80 in the rear wall of its

baseplate

42b, 44b which accommodatingly receives the stripped terminal end portion of the

leads

60b, 62b respectively. The bores 80 extend inwardly along the longitudinal axis of each baseplate.

A setscrew 82, extending in a tapped transversepassageway running from a sidewall of the baseplates to the bore'80 bears against the end portions of the leads totightly engage" the leads.

A further feature of the invention is the fact that the

jaw members

38, 40 may be easily replaced if the spike tips of the protuberances 46 become damaged. In fact, one advantage of the present invention is that because the clamp arms are constructed of a synthetic plastic which'has desirable insulating characteristics, there is no need to provide insulating washers and bushings to isolate the jaw members from the body of the clamp.

Thus it will be seen that there has been provided a vehiclegrounding clamp which fulfills the stringent safety'requirements of tank vehicles loading operations and is easy to operate and maintain.

As various possible embodiments might be made of the present invention, and as various changes might be made in .the embodiments above set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

What is claimed is: V

l. A clamp for grounding flammable-liquid-transporting vehicles and dissipating any electrostatic charges carried by the vehicle, said clamp comprising a body, said body including two jaw portions, means for moving said portions relative to one another, means biasing the jaw portions toward one another, a jaw contact member for each jaw portion, the jaw portions including means for receiving its associated jaw contact member, each jaw portion being constructed of one "piece molded synthetic plastic, electrical lead means, the electrical lead means extending from an electrostatic drain device to each jaw contact member whereby a series electrical circuit may be completed from each lead through the respective jaw contact member and through an electrically conducting portion of the vehicle body to drain any electrostatic charge 'carried by the vehicle during a flammable-fluidloading opera tion, wherein the body is formed of two arms, means pivotally interconnecting the arms intermediate the ends thereof, 'each arm including a handle portion adjacent one end thereof and on a common side of the means pivotally interconnecting the arms, the jaw portions being formed in each arm on theopposite side of the means pivotally interconnecting the arms, each arm being of one-piece molded synthetic plastic construction, wherein the means biasing the jaw portions toward one another includes a helical coil spring, the means pivotally interconnecting the arms includes a pin, the helical coil spring having convolutions which extend substantially concentrically about the pin, wherein each jaw contact member includes a baseplate and a plurality of spiked protuberances projecting therefrom, means mounting the jaw contact members in the means receiving the jaw contact members, the mounting means including a plurality of bolts, each of said bolts having a spiked tip, the bolts having their longitudinal axis in substantially perpendicular relationship to the base plate, the bolts extending from the jaw portions through the baseplate and outwardly therefrom, the portion of each bolt extending outwardly from its respective baseplate forming the spiked protuberance, and the jaw contact members being formed of metal in a one-piece construction, whereby the spiked protuberances may readily engage an electrically conducting portion of the vehicle body.

2. A clamp constructed in accordance with claim 1 wherein means forming a plurality of parallel spaced grooves across one of the handle portions in a direction transverse to the length thereof is provided, whereby the manual grasping of the handle portion is facilitated by the placement of the user's fingers within selected grooves.

3. A clamp constructed in accordance with claim 1 wherein the spiked protuberances in one jaw contact member extends along the longitudinal axis of the one contact member and the member, the spiked protuberances of the other contact member being grouped in pairs with each pair lying in a plane transverse to the longitudinal axis of the other contact member base and an associated spiked protuberance of the one jaw contact member lying in the same transverse plane whereby at least three-point mechanical contact may be made between the respective jaw contact members over an electrically conductive curved surface of the vehicle.

4. A clamp constructed in accordance with claim 1 wherein shims are provided, said shims being spaced between the baaeplate of each jaw contact member and the means receiving each' jaw contact member, whereby the tips of the spiked protuberances of the respective jaw contact members may be positioned in substantially parallel relationship.

5. A clamp constructed in accordance with claim 1 wherein means for adjustably varying the length of each spiked protuberance is provided, said adjustment means comprising shim washers, said shim washers being spaced between the heads of the bolts and the jaw portions to vary the effective length of each bolt.

6. A clamp constructed in accordance with claim 1 wherein means is provided for automatically disconnecting the electrical lead means between the electrostatic drain device'and the I clamp if the vehicle is inadvertently moved while the clamp is still affixed to the vehicle, said automatic disconnecting means I comprising a snap apart electrical connector, said electrical connector being positioned in the lead means intermediate the clamp and the electrostatic drain device. I

7. A clamp constructed in accordance with claim 1 wherein coupling means is provided to mechanically interconnect each jaw contact member and the electrical lead means, the

Claims

1. A clamp for grounding flammable-liquid-transporting vehicles and dissipating any electrostatic charges carried by the vehicle, said clamp comprising a body, said body including two jaw portions, means for moving said portions relative to one another, means biasing the jaw portions toward one another, a jaw contact member for each jaw portion, the jaw portions including means for receiving its associated jaw contact member, each jaw portion being constructed of one piece molded synthetic plastic, electrical lead means, the electrical lead means extending from an electrostatic drain device to each jaw contact member whereby a series electrical circuit may be completed from each lead through the respective jaw contact member and through an electrically conducting portion of the vehicle body to drain any electrostatic charge carried by the vehicle during a flammablefluid-loading operation, wherein the body is formed of two arms, means pivotally interconnecting the arms intermediate the ends thereof, each arm including a handle portion adjacent one end thereof and on a common side of the means pivotally interconnecting the arms, the jaw portions being formed in each arm on the opposite side of the means pivotally interconnecting the arms, each arm being of one-piece molded synthetic plastic construction, wherein the means biasing the jaw portions toward one another includes a helical coil spring, the means pivotally interconnecting the arms includes a pin, the helical coil spring having convolutions which extend substantially concentrically about the pin, wherein each jaw contact member includes a baseplate and a plurality of spiked protuberances projecting therefrom, means mounting the jaw contact members in the means receiving the jaw contact members, the mounting means including a plurality of bolts, each of said bolts having a spiked tip, the bolts having their longitudinal axis in substantially perpendicular relationship to the base plate, the bolts extending from the jaw portions through the baseplate and outwardly therefrom, the portion of each bolt extending outwardly from its respective baseplate forming the spiked protuberance, and the jaw contact members being formed of metal in a one-piece construction, whereby the spiked protuberances may readily engage an electrically conducting portion of the vehicle body.

2. A clamp constructed in accordance with claim 1 wherein means forming a plurality of parallel spaced grooves across one of the handle portions in a direction transverse to the length thereof is provided, whereby the manual grasping of the handle portion is facilitated by the placement of the user''s fingers within selected grooves.

3. A clamp constructed in accordance with claim 1 wherein the spiked protuberances in one jaw contact member extends along the longitudinal axis of the one contact member and the spiked protuberances of the other jaw contact member are spaced from the longitudinal axis of the other contact member, the spiked protuberances of the other contact member being grouped in pairs with each pair lying in a plane transverse to the longitudinal axis of the other contact member base and an associated spiked protuberance of the one jaw contact member lying in the same transverse plane whereby at least three-point mechanical contact may be made between the respective jaw contact members over an electrically conductive curved surface of the vehicle.

4. A clamp constructed in accordance with claim 1 wherein sHims are provided, said shims being spaced between the baseplate of each jaw contact member and the means receiving each jaw contact member, whereby the tips of the spiked protuberances of the respective jaw contact members may be positioned in substantially parallel relationship.

6. A clamp constructed in accordance with claim 1 wherein means is provided for automatically disconnecting the electrical lead means between the electrostatic drain device and the clamp if the vehicle is inadvertently moved while the clamp is still affixed to the vehicle, said automatic disconnecting means comprising a snap apart electrical connector, said electrical connector being positioned in the lead means intermediate the clamp and the electrostatic drain device.

7. A clamp constructed in accordance with claim 1 wherein coupling means is provided to mechanically interconnect each jaw contact member and the electrical lead means, the coupling means including means forming a bore in each jaw contact member, the electrical lead means including two electrical leads, an electrical lead extending into each bore, the coupling means further including means forming a transverse passageway in each jaw contact member, each of said passageways extending into its respective bore, each passageway including a setscrew, the setscrew bearing against the electrical lead seated within the bore.