Field of the I nvention

[1] This invention relates general ly to a type of weight ba lancing gantry for balancing industrial tools, such as spot-welding guns.

Backgrou nd of the I nvention

[2] Weight balancing ga ntries are used in industry to vertically balance the weight of industrial tools, such as spot-welding guns in the car repair industry. The weight of these tools can range from 10-25kgs depending on arm size used, making them heavy and awkward to use without the assistance of a weight balancing gantry.

[3] US 2176979 A (Platz) 24 October 1939 discloses a typical weight balancing gantry arrangement comprising a horizontal radial arm supported from a tower. A bogey runs along the horizontal radial arm and has pneumatic counterbalancing mechanism thereon from which a spot-welding gun is vertically balanced from a cable.

[4] US 6087611 A (De Bruyn et al.) discloses a system for vertical ly balancing welding tongs which comprises a spring balance attach ed from a horizontal radia l arm for supporting the welding tongs from a cable. In a similar manner as that taught by Platz, the spring balance can run along the horizontal radial arm to various horizontal positions.

[5] However, when welding within the beaver panel (section under the boot l id and boot floor) of a vehicle for exam ple, the cable may be obstructed by the boot lid . Furthermore, the height of the roof of the vehicle may be too high for the radial arm.

[6] As such, a need exists for an im proved weight balancing gantry which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[7] It is to be understood that, if a ny prior art information is referred to herein, such reference does not constitute an adm ission that the information forms part of the com mon general knowledge in the art, in Austral ia or any other country.

Summa ry of the Disclosure

[8] There is provided herein a weight balancing gantry comprising a tower having a fixed length radial arm pivotally coupled from a pivot point at an upper end thereof. An angle strut acts between the tower and the radial arm across the pivot point to adjust t he angle of the radial arm with respect to the tower. The pivot point pul ley is located at the upper end of the tower. [9] The gantry may be supported from a n industrial cart and the gantry supports an associated industrial tool from the radial arm . The industrial cart may be a m obile spot welder and the ind ustria l tool may be a spot-welding gun.

[10] The gantry further comprises a weight balancing mechanism which may com prise pneumatically biased opposing pul leys.

[11] Furthermore, the gantry com prises a positioning mechanism at the radial arm com prising at least one controlled cylinder for positioning and holding the bogey along the radial arm .

[12] The cable is run from the weight bala ncing mechanism, up across the pivot point pulley and over the bogey pulley to attach to the industrial tool for the balancing thereof.

[13] The length of the ca ble is determ ined such that, in the manner shown in Figure 1, when the positioning mechanism is retracted, the length of ca ble between the bogey pul ley and the industria l tool is lengthened so as to position the industrial tool at a lower proximal stowed position. The industrial cart may com prise a tool holder such that, when the industrial tool is at the lower proximal stowed position, the industrial tool can be easily be placed in the holder.

[14] Flowever, when the positioning mechanism is extended, the length of cable between the bogey pulley and the industrial tool shortens to move the industrial tool to a distal raised deployed position.

[15] In the manner shown in Figure 2, the radial arm can be raised by the angle strut to hoist the industrial tool over a high obstacle, such as a vehicle roof. When the radial arm is inclined at an angle in this way, the at least one cylinder of the positioning mechanism holds the bogey in place along the radial arm and prevents the bogey from running down the radial arm.

[16] In the manner shown in Figure 3, the radial arm may be lowered, and the bogey positioned at a distal end of the arm to reach under an overhanging obstacle such as vehicle boot when working on the beaver panel for example.

[17] Furthermore, the fixed length radial arm having the bogey travelling therealong, sim pl ifies the construction of the radial arm and increases the resilience and weight bearing structural integrity thereof.

[18] The weight balancing mechanism may comprise collinear cylinders to reduce the width of the tower.

[19] Furthermore, the positioning mechanism may comprise two cylinders acting in series wherein a piston rod of a proximal cylinder of the positioning mechanism is connected to the cylinder tube of a distal cylinder of the positioning mechanism so that the bogey can be brought close to the tower, such as, for example, for placing the spot welder in a holder of the industrial cart.

[20] Other aspects of the invention are also disclosed.

Brief Descri ption of the Drawings

[21] Notwithstanding any other forms which may fal l within the scope of the present invention, preferred em bodiments of the disclosure will now be described, by way of exam ple only, with reference to the accompanying drawings in wh ich :

[22] Figure 1 shows a weight balancing gantry in accordance with an embodiment;

[23] Figure 2 illustrates the raising of a radial arm of the gantry to reach over high objects; and

[24] Figure 3 illustrates the lowering of the radial arm of the gantry to reach under objects.

Description of Em bodiments

[25] A weight balancing gantry 100 comprises a tower 101 having a radial arm 102 pivotally coupled from a pivot point 104 at an upper end of the tower 101 for supporting a n industrial tool 109 such as a spot-welding gun .

[26] The gantry 101 may be supported from a n industrial cart 113 having castor wheels 114, such as a mobile spot welder.

[27] An angle strut 116 acts between the tower 101 and the radial arm 102 across the pivot point 104.

[28] In em bodiments, the radial arm 102 may further swing side to side.

[29] The gantry 100 com prises a weight balancing mechanism 110 which may comprise counteracting weight balancing pul leys 117. Each pul ley 117 may be pneumatically biased from respective pneumatic cylinders 111, preferably in-line in the manner shown in Figure 1 to reduce the overal l width of the tower 101. In the em bodiment shown, the weight balancing mechanism 110 is concealed within the tower 101.

[30] In an embodiment, the balancing mechanism 110 may comprise a cheaper spring balancer as opposed to the pneumatic balancing cylinders.

[31] A bogey 107 runs along the radial arm 102 between proximal and distal positions and supports a bogey pulley 108. The bogey 107 may run within an interior of the radial arm 102 in em bodiments. A pivot point pul ley 103 is located between the tower 101 and the radial arm 102, preferably coaxial with the pivot point 104. [32] The positioning mechanism 106 may com prise at least one controlled cylinder 105 which acts between the radial arm 102 and the bogey 107 to position and hold the bogey 107 at various positions along the radial arm 102.

[33] The at least one cylinder 105 may be a pneumatic cyl inder but, in alternative embodiments, may be hydraulic for increased p ositional stabil ity, especial ly when the radia l arm 102 is at an angle.

[34] As spot welder guns al ready have an air supply (to al low the electrodes in the gun to squeeze the metals therefrom for welding), the air supply may be routed to the at least one cylinder of the positioning mechanism 106 by an offtake. As such, when the industrial tool is activated, the positioning mechanism automatically extends. A one-way valve may interface the offtake such that, should the air supply the accidental ly disconnected, th e positioning mechanism 106 remained extended.

[35] A pneumatic toggle switch may allow forward and backward control of the at least one cylinder 105 of the positioning mechanism 106. When the toggle switch is opened, the cylinders 105 extend and are held extended by a pressure against gravity and cable tension.

[36] Typically however, the toggle switch may only allow positioning between fully extended and ful ly retracted positions and, as such, in a n em bodiment, a control solenoid may be em ployed for inching control can be achieved should cylinder positioning be required.

[37] A cable 118 may be run from between the cylinders 111 of the balancing mechanism 110, over the upper weight balancing pulley 117, down round the lower weight balancing pulley 117, up across the pivot point pulley 103, across to the bogey pulley 108 and down to support the industrial tool 109 at a distal end thereof.

[38] In the em bodiment shown, a pair of cylinders 105 act in series along the radial arm 102. In em bodiments shown, the piston rod of the proximal cylinder 105 is connected to the cylinder tube of the distal cylinder 105 such that the cyl inders 105 can assume contracted length substantially equal to that of one of the cylinder tubes, especially helpful when positioning the tool 109 into a toolholder on the cart 113.

[39] With reference to Figure 1, the length of cable 118 is determined such that, when the cylinders 105 of the positioning mechanism 106 are retracted, the length of cable 118 between the bogey pulley 108 and the industrial tool 109 is lengthened so as to hold the tool 109 at a lower proximal stowed position 120. However, when the cylinders 105 of the positioning mechanism 106 are extended, the length of cable 118 between the bogey pulley 108 and the industria l tool 109 shortens so a s to hold the tool 109 at an upper distal position 119 at the end of the radial arm 102 ready for use.

[40] In embodiments, the cart 130 may com prise a toolholder 112 which corresponds generally with the lower proximal stowed position 120. As such, when the po sitioning mechanism 106 is retracted, the industrial tool 109 may be easily placed within the toolholder 112.

[41] In an embodiment (not shown) the tower 101 may be extendable in comprising a height adjustment mechanism com pris ing a cylinder 112 acting between a base piece 113 and an upper moveable telescopic piece. The height adjustment mechanism may be used in conjunction was alternative to the pivoting radial arm 102 wherein, for the latter, the radial arm 102 can be fixed at a right angle and height can be a djusted using the height adjustment mechanism . The height adjustment mechanism may be controlled by a linear actuator as opposed to a cylinder for torque and lock enhancement . Similarly, the l inear actuator may be used for the angle strut 116 as opposed to a cylinder for enhanced angle control and lockability.

[42] Where the angle strut 116 comprises a gas strut, the angle strut 116 may be lockable for holding the radial arm 102 in place at a certain height.

[43] In embodiments angle strut 116 may com prise remotely controlled pneumatic cylinder, preferably controlled from the industrial tool 109.

[44] The gantry 100 may comprise controllers accessible at the industrial tool 109 (wired or wireless) to control actuators for the angle strut 116 and positioning mechanism 106.

[45] Furthermore, pressure within a pressure tank operably coupled to the pneumatic cylinder 111 of the weight balancing mechanism 110 may be adjusted (either manually or using an actuator) to match the weight of the industrial tool 109.

[46] A separate supply from the same air supply source may be connected to the balancing cyl inders 111 and final ly to the pressure tank from a one-way valve and an air adjusting valve for adjusting tension the tension of the cable 118.

[47] As such, in the manner shown in Figure 2, the radial arm 102 may be raised by controlling the angle strut 116 to avoid an elevated obstacle 121. The cylinders 105 of the positioning mechanism 106 hold the bogey 107 in place along the radial arm, preventing the bogey 107 from sl iding down the radial arm 107.

[48] In the manner shown in Figure 2, the radial arm 102 may be raised to reach over high obstacles 121 and lowered in the manner shown in Figure 3 to reach under overhanging obstacles 120. [49] In em bodiments, where the angle strut 116 com prises a gas strut, the angle strut expands at the force rating thereof. A spring-loaded pin in the strut 116 may be pushed by a pivoting lever handle to lock the strut 116 at different positions. When the lever is pulled, the strut 116 may be released up to the maximum stroke thereof. A handle of the lever may be at one end of the strut 116 mounted on a bracket on the tower and the handle may be pushed and held in a downward position to release the lock to allow movement of the arm 102 in either direction then released to hold it at the desired angle.

[50] The force rating of the strut 116 may be such that when the tool 109 is at the proximal position 120, the force rating may be sufficient to raise the radial arm to the maxim um angle thereof when the strut 116 is unlocked. Conversely, when the tool 109 is at the distal position 119, the force rating may be insufficient such that the radial arm 102 lowers.

[51] As such, the raising and lowering of the radial arm 102 may be controlled by the position of the bogey 107.

[52] When raising the rad ial arm 102, the positioning mechanism 106 may be retracted and the tool 109 placed in the holder 112 where after the strut 116 may be unlocked to raise the radial arm 102.

[53] However, as the length of cable 118 may position the tool 109 beneath the holder 112 because the radial arm 102 is lowered and thereby requiring the operator to lift the tool, as an alternative, to allow support of the weight of the tool 109 all the way to the holder 112, the operator may push the radial a rm 102 up at the same time while retracting the positioning cylinders such that, when the tool 109 reaches the holder 112, the radial arm 102 will already be at the highest position thereof.

[54] As the lever to unlock the strut 116 may be spring loaded (i.e., in that the handle thereof needs to be held down to unlock the strut 116), it may be difficult to hold the tool 109 up and the lever down sim ultaneously, especially when the operator is at the distal end away from the lever.

[55] As such, the mechanism to unlock the strut 116 may be modified to hold the strut 116 unlocked wherein the handle may be pushed down and then inward to be held in place . The radial arm 102 can now be automatically raised from is lower position by the force of the strut 116 while it is unlocked by simply retracting the positioning cylinders, shifting the weight of the tool 109 back toward the pivotal end, completely supporting the weight of the tool 109 all the way to the holder. The operator then pulls the lever outward to then relock the strut 116. [56] If a remotely controlled pneumatic cyl inder (coupled with a standard gas strut for assistance) is used for the angle strut 116 the height of the radial arm 102 may be adjusted when the tool 109 is at the distal end of the radial arm 102.

[57] The foregoing description, for purposes of expla nation, used specific nomenclature to provide a thorough u nderstanding of the invention. However, it will be apparent to one skil led in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific em bodiments of the invention are presented for purposes of ill ustration and description. They are not intended to be exhaustive or to lim it the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applica tions, thereby enabling others skilled in the art to best util ize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the fol lowing claims and their equivalents define the scope of the invention.

[58] The term "approximately" or sim ilar as used herein should be construed as being within 10% of the value stated unless otherwise indicated.