Field of the Invention

The present invention relates to a linear actuator assembly, and in particular to a linear actuator assembly incorporating hydraulic cylinders. More particularly, the present invention relates to a hydraulic cylinder actuator assembly for use in a metal pressing process.

Description of the Related Art

Linear actuators are mechanisms that produce linear forces. Linear actuators have utility in a wide range of applications, notably in industrial machinery, for automated movement of components of the machinery or for damping such components. Two types of linear actuator of particular interest are hydraulic cylinders and pneumatic cylinders. Hydraulic and pneumatic cylinders use a working fluid, in the case of a hydraulic cylinder typically a hydraulic oil and in the case of a pneumatic cylinder typically an inert gas, to control the movement of a piston either outwardly (or inwardly) of a cylinder portion.

One particular use of a hydraulic or pneumatic cylinder is in metalpressing/stamping machinery. In such a use, a‘spring’ type pneumatic cylinder is typically referred to as a‘gas spring’.

In a typical mechanical press used in a metal pressing process, the ram drives the upper die part of a press tool downwardly towards the lower die part of the press tool, and the workpiece, or‘blank’, is supported therebetween by the blank-holder. The function of the blank-holder is generally to hold the workpiece in place during the pressing operation and to auto-lift the pressed workpiece from the lower die following pressing. The blank-holder typically takes the form of a clamp about the perimeter of the workpiece.

Whilst the position of the lower die is generally fixed, the blank-holder is usually configured to be movable so as to allow the upper die to engage the workpiece at a position a short distance above the lower die, and to allow the workpiece to then travel downwardly with the upper die before contacting the lower die. A‘press-cushion’ (also called a‘die’ or‘bed’ cushion) is conventionally provided under the blank-holder. The primary function of the press cushion is to provide a flexible, controlled, blank-holder force, to control material flow of the workpiece during the pressing operation.

Typically such a press-cushion comprises of a single motor unit, often an air-bag, equipped with a plurality of cushion pins for engaging the blank-holder at different locations. As will be appreciated, it is often the case that a single press machine may be used for pressing of different parts, and so the cushion pins may be moved to engage the blank-holder at different locations to facilitate localized control of the blank-holder force to optimise material flow to suit the particular shape of the pressing. Although such conventional press cushions are generally effective, they incur certain practical disadvantages, and so in certain applications it may be desirable to replace such a press cushion with an array of hydraulic cylinders or gas springs.

The replacement of such press cushions with hydraulic cylinders or gas springs overcomes many of the problems encountered with conventional press cushions and it is known that hydraulic cylinders/gas springs function effectively in substitute of a conventional press cushion. However, whilst the function of conventional hydraulic cylinders/gas springs is satisfactory for use in substitute of a press cushion, their construction does not lend itself so readily to such a use. In particular, problems are encountered using hydraulic cylinders/gas springs in substitute of a press cushion on a pressing machine used for multiple different pressings where different blank-holder force distribution patterns are required.

Existing hydraulic cylinders/gas springs of the prior art comprise generally of a single piece housing defining internally a chamber within which a piston reciprocates, and including a fluid inlet/outlet port defined by the housing permitting charging of the chamber with a working fluid. The housing is usually bolted to a bed of the pressing machine. When used as a press cushion, the plurality of hydraulic cylinders/gas springs in an array are typically fluidly coupled to a central control unit by hard pipes carrying the working fluid under elevated pressure conditions.

However, in such a use of hydraulic cylinders/gas springs a problem is encountered inasmuch that, following pressing of a first part, to re-purpose the pressing machine for pressing of a differently shaped part requiring a different distribution of blank-holder force, it is necessary to reconfigure the hydraulic cylinders/gas springs, by unbolting the hydraulic cylinders/gas springs from their original position and reattaching them to the bed at a new position, and subsequently reconfiguring the fluid supply pipes. It will be appreciated that this method of repositioning hydraulic cylinders/gas springs incurs significant time costs and can result in an (often expensive) pressing machine standing redundant whilst an operative reconfigures the hydraulic cylinders/gas spring array.

Furthermore, the material being worked on in the metal pressing processes may be required to go through a number of stages to achieve the required final state. This may require the use of one or more press tools to achieve the required stages. The changing of press tools can result in downtime which incurs significant time costs replacing the press tool and can result in an (often expensive) pressing machine standing redundant whilst the press tool is being replaced.

It is desirable therefore to provide a linear actuator assembly, and more particularly a linear actuator assembly incorporating two or more hydraulic cylinders, having a construction which obviates the aforementioned problems encountered with conventional linear actuator assemblies.

Brief Summary of the Invention

According to a first aspect of the invention there is provided a linear actuator assembly comprising:

a plurality of hydraulic cylinders;

a manifold block in fluid communication with at least one of said plurality of hydraulic cylinders;

a control block in fluid communication with the manifold block, and arranged to be in fluid communication with said at least one of said plurality of hydraulic cylinders via said manifold block, said control block comprising a fluid passageway running therethrough having a first end and a second end;

an accumulator in fluid communication with said control block, and arranged to be in fluid with the manifold block via said control block; and a first coupling arrangement having a quick disconnect, said first coupling arrangement configured to couple the control block to the to the manifold block.

A linear actuator assembly in accordance with the invention allows the components of the linear actuator assembly upstream of the control block to be easily disconnected from the control block and the components downstream of the control block. This reduces the downtime incurred in replacing a press tool or the components of the press tool.

Preferably, the first coupling arrangement further comprises a hose section fluidly connecting the control block to the manifold block, said hose section having a quick disconnect positioned at an end thereof.

The hose section of the first coupling arrangement allows the control block and the components of the linear actuator assembly downstream of the control block to be positioned as a more convenient location relative to the metal-pressing/stamping machinery. This is advantageous in situations where floor space for the press metal-pressing/stamping machinery is limited.

In exemplary configurations, the first coupling arrangement comprises a quick disconnect positioned at each end of the hose section.

Preferably, the linear actuator assembly further comprises a second coupling arrangement including a quick disconnect, said second coupling arrangement configured to couple the control block to the accumulator.

Preferably, the control block is directly coupled to the accumulator by the quick disconnect of the second coupling arrangement.

In exemplary configurations, the second coupling arrangement further comprises a hose section fluidly connecting the control block to the accumulator, said hose section having a quick disconnect position at an end thereof.

Preferably, the control block comprises a first valve means configured to control the flow of fluid from the manifold block into the control block, and a second valve means configured to allow the flow of fluid from the control block into the manifold block.

In exemplary embodiments, the first valve means comprises a force generator valve, and the second valve means comprises a solenoid valve.

Preferably, the linear actuator assembly, further comprises a third coupling arrangement including a quick disconnect, said third coupling arrangement configured to couple the at least one of said plurality of hydraulic cylinders to the manifold block.

In exemplary embodiments, the third coupling arrangement comprises a hose section fluidly connecting at least one of said plurality of hydraulic cylinders to the manifold block, said hose section having a quick disconnect positioned in at least one end thereof.

Preferably, the third coupling arrangement comprises a quick disconnect position at each end of the hose section.

According to a second aspect of the invention, there is provided a metal press linear actuator system comprising:

a first unit arranged to be mounted on a section of a press tool;

a second unit configured to be positioned at a distance from the press tool; and

a coupling arrangement having a hose section and a quick disconnect positioned at an end of the hose section, said coupling arrangement configured to connect the first unit to the second unit,

wherein said first unit includes a plurality of hydraulic cylinders and a manifold block connected to said plurality of hydraulic cylinders,

and said second unit includes a control block and an accumulator connected to the control block.

With the linear actuator system of the invention, the control block and accumulator components are not housed in or located with the press tool. This is advantageous in that the press tool does not needed to be designed in such a way to accommodate these components and as such the overall footprint of the press tool will be smaller than one which incorporates a control block and accumulator therein.

In addition, the capital outlay by a user is significantly reduced as he/she requires only a single accumulator and control block assembly which can be used with different press tools.

Preferably, the first unit is incorporated in the press tool.

Preferably, the control block comprises a first valve means configured to control the flow of fluid from the manifold block into the accumulator via the control block, and a second valve means configured to control the flow of fluid from the accumulator via the control block into the manifold block.

Preferably, the first valve means comprises a force generator valve, and the second valve means comprises a solenoid valve.

According to a third aspect of the present invention, there is provided a press tool for use within a metal press linear actuator system in accordance with the second aspect of the invention.

Other aspects of the invention are as set out in the claims herein.

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Fig. 1 shows a metal press incorporating a press tool as known in the art;

Fig. 2 shows a first embodiment of a linear actuator assembly in accordance with the invention; Fig. 3 is a side view an alternative arrangement of a linear actuator assembly in accordance with the first embodiment;

Fig. 4 is a cross-sectional view of the arrangement of fig. 3;

Fig. 5 shows an alternative arrangement of a linear actuator assembly in accordance with the first embodiment;

Fig. 6 is a side view a linear actuator assembly in accordance with the second embodiment of the invention;

Fig. 7 is a cross-sectional view of the arrangement of fig. 6;

Fig. 8 is a schematic view of an alternative manifold/hydraulic cylinder arrangement forming part of a linear actuator assembly in accordance with the invention;

Fig. 9a to 9f show the working of the linear actuator assembly during the compression of the gas spring(s);

Fig. 10a to 10d show the working of the linear actuator assembly to return the gas spring(s) to their uncompressed state; and

Figs. 11a and 11 b show a metal press incorporating a linear actuator system in accordance with the invention.

Detailed Description of the Embodiments

There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description

Aspects of the present invention relate to an improved construction of a linear actuator assembly. The linear actuator assembly in accordance with specific embodiments of the invention described herein in incorporates linear actuators in the form of a hydraulic cylinder.

One use for such a linear actuator assembly that is of particular interest to the present applicant is an assembly for supporting a blank-holder in a metal pressing machine (herein after referred to as a metal press). Thus, in the specific embodiment described herein, the linear actuator assembly is one which incorporates a hydraulic cylinder suitable for exerting a force on a blank-holder resting thereon in a metal press. It will of course be appreciated however that, although the specific embodiment of the invention described herein incorporates a hydraulic cylinder suitable for exerting a force on a blank-holder resting thereon in a metal press, the invention could alternatively embody an alternative type of linear actuators for a different application, for example, in an alternative embodiment the invention may incorporate a hydraulic ‘ram’ cylinder. Moreover, it will be appreciated that hydraulic cylinders, and linear actuators more generally, have utility in a number of different applications other than for supporting a blank-holder in a metal press, and it should be understood that the invention is not limited in this regard to any one particular intended application rather has broader utility.

Referring to fig. 1 , a metal press 1 incorporating a press tool 2 as known in the art is shown.

The press tool 2 includes a top plate 3 and a bottom plate 4. The top plate 3 is attached to the metal press 1 such that it can be actuated for movement towards the bottom plate 4.

The top plate 3 carries upper die part which generally includes the trust plate 5, the punch holder (not shown), and the punch (not shown) components of the press tool.

The bottom plate 4 carries the lower die part which generally includes the die plate (not shown), the stripper or blank holder (not shown), and the hydraulic cylinders/gas springs type linear actuator assembly (not shown) components of the press tool.

The size and footprint of the press tool 2 is influenced by the linear actuator assembly incorporated therein. This means that for some applications, a large area is needed to accommodate both the metal press and the press tool.

Referring to Figs. 2 to 4, a first embodiment of a linear actuator assembly 100 in accordance with the invention will now be described.

The linear actuator assembly 100 comprises a plurality of linear actuators in the form of hydraulic cylinders 110.

As known in the art, each of the hydraulic cylinders 110 comprises piston 111 and a chamber 112. The chamber 112 is filled with a working fluid in the form of oil. The piston 111 of each hydraulic cylinder 110 is arranged such that it can slide into and out of the chamber 112 while maintaining a seal such that the oil within the chamber 112 does not leak out via the piston 111.

The plurality of hydraulic cylinders 110 are configured for use in substitute of a press cushion in metal pressing machinery. Thus, in the example arrangement, the function of the plurality of hydraulic cylinders 110 is to exert a retarding and restorative force on a blank-holder, supported on said hydraulic cylinders 110, in order to control the flow of a workpiece (typically a flat metal sheet) held by the blank-holder during a pressing operation.

The hydraulic cylinders 110 are each connected to a manifold block 120 of the linear actuator assembly 100 by a respective coupling arrangement 130.

In the embodiment shown, the manifold block 120 is in cuboid in shape and has ten connection points/ports 121. It would be understood that the manifold block 120 may be of a different shape and may have more or less than ten connection points/ports 121.

Each cylinder-manifold coupling arrangement 130 includes a hose section 131 which is configured to fluidly connect an associated hydraulic cylinder 110 to the manifold block 120, and a quick disconnect 132, 133 (see Fig. 4) positioned at each end thereof of the hose section 131. The quick disconnects 132, 133 are adapted to connect the hose section 131 to a respective hydraulic cylinder 110 at one end thereof and to the manifold block 120 at an opposite end thereof.

The quick disconnects 132, 133 provide a fast, make-or-break connection of the fluid transfer line formed by each the hose sections 131 between the hydraulic cylinders 110 and the manifold block 120.

A control block 140 is connected to the manifold block 120 such that it is in fluid communication with the manifold block 120. In this way, the control block 140 is in fluid communication with the hydraulic cylinders 110 via said manifold block 120.

In the embodiment shown, the control block 140 is connected to the manifold block 120 by a coupling arrangement 150.

The manifold-control block coupling arrangement 150 is similar to the cylinder-manifold coupling arrangement 130. The manifold-control block coupling arrangement 150 comprises a hose section 151 which fluidly connects the control block 140 to the manifold block 120, and a quick disconnect 152, 153 positioned at each end of the hose section 151 adapted to connect the hose section 151 to the control block 140 at one end thereof and to the manifold block 120 at an opposite end thereof.

The quick disconnects 152, 153 to provide a fast, make-or-break connection of the fluid transfer line formed by the hose section 151 between the control block 140 and the manifold block 120.

While the manifold-control block coupling arrangement has been described with a quick disconnect positioned at either end of the hose section, it is only essential that one of the ends of the hose section includes a quick disconnect.

The control block 140 has a fluid passageway 141 running therethrough. A first end 1411 of the fluid passageway 141 is configured to receive the quick disconnect 153 at the end of the hose section 151.

The fluid passageway 141 has first and second flow channels1413, 1414 located between its first end 1411 and a second end 1412 thereof.

The control block 140 comprises a first valve means 142 configured to close and open the first flow channel 1413 of the fluid passageway 141 , and a second valve means 143 configured to close and open the second flow channel 1414 of the fluid passageway 141.

In the embodiment shown, the first valve means 142 is arranged to control the flow of fluid from the manifold block 120 into an accumulator 160 via the control block 140, and the second valve means 143 is arranged to control the flow of fluid from the accumulator 160 into the manifold block 120 via the control block 140.

The first valve means 142 is in the form of a force generator valve, and the second valve means 143 is in the form of a solenoid valve. It would be understood that the first and second valve means may be other suitable valve means in the art which achieve the intended purpose of the force generator valve 142 and the solenoid valve. In an unactuated state (see Fig. 4), the force generator valve 142 blocks the first flow channel 1413 thus preventing the flow of fluid through the first flow channel 1413. The force generator valve 142 is actuated to unblock the first flow channel 1413 when a force acting on the force generator valve 142 exceeds a predetermined or default value PD.

The control block 140 includes a pressure valve 144 which is configured to set and/or adjust the predetermined/default value PD of the force required to actuate the force generator valve 142.

Similarly, in an unactuated state (see Fig. 5), the solenoid valve blocks the second flow channel 1414 thus preventing the flow of fluid through the second flow channel 1414. The solenoid vale is actuated by an electrical signal as known in the art.

The accumulator 160 is positioned in fluid communication with the control block 140, and is coupled to the control block 140 at the second end 1412 of the fluid passageway 141 by a coupling arrangement 170.

The control block-accumulator coupling arrangement 170 is different to the previously described coupling arrangements 130, 150 in that it does not comprise a hose section. The control block-accumulator coupling arrangement 170 is a quick disconnect 171 (see Fig. 4) adapted to connect the control block 140 to the accumulator 160. It would be understood that a different coupling arrangement which includes a hose section may be utilized instead.

The accumulator 160 is in the form of a compressed gas/hydro-pneumatic accumulator having a first chamber 161 adapted to receive a fluid, and a second sealed chamber 162 filled with a compressible gas, for example nitrogen.

In the embodiment shown, the compressed gas accumulator 160 is in the form of a piston accumulator having a movable piston 163 separating the first chamber 161 from the second chamber 162. The second chamber is filled with nitrogen which is configured to be compressed to a pressure of 10-20 bar. This is advantageous in that it does not put undue pressure on the seals of the movable piston 163 or in the accumulator 160.

Fig. 5 shows an alternative arrangement of the components forming the linear actuator assembly 100 in accordance with a first embodiment the invention.

Due to the fact that the main components of the linear actuator assembly 100 are connected to one another by quick disconnects, the assembly is quite versatile in its configuration. In addition, the linear actuator assembly may be easily assembled and disassembled as required, and the parts can be easily moved to any location within a factory or workshop.

Referring to Figs. 6 and 7, a second embodiment of a linear actuator assembly 200 in accordance with the invention is shown.

The linear actuator assembly 200 is similar to that of the first embodiment previously described with the numerals for similar features to that of the first embodiment increased by 100 for ease of reference, for example the hydraulic cylinders which were referred to with reference numeral 1 10 in the first embodiment will be referred to with reference numeral 210.

The differences between the linear actuator assembly 200 of the second embodiment and that of the first embodiment 100 will now be described.

The second embodiment differs from the first embodiment in that the manifold block 220 is directly coupled to the control block 240 without the use of a coupling arrangement.

Referring to fig 8, an alternative manifold/hydraulic cylinder arrangement is shown.

In this configuration, the hydraulic cylinders 310 are nested in the manifold block 320 in predetermined and fixed configuration.

The manifold block 320 may be connected to the control block via coupling arrangement with a hose section 330 in a similar manner as previously described.

Referring to Figs. 9a to 9f, the working of the first embodiment of the linear actuator assembly 100 in accordance with the invention will now be described. The second embodiment 200 works in a similar fashion to that of the first embodiment.

The linear actuator assembly 100 is first primed with the working fluid 180 i.e. oil, to a required pressure Po as known in the art.

For ease of explanation, pressures of the working fluid in various areas of the linear actuator assembly will be denoted with the following symbols:

Pi - pressure in the hose section 131

P ₂ - pressure in the hose section 151

P3 - pressure in the portion of the fluid passageway 141 between the first end 1411 of the fluid passageway 141and the valve means 142, 143

P ₄ - pressure in the portion of the fluid passageway 141 between the valve means 142, 143 and the second end of the fluid passageway . The pressures Pi, P ₂ , P ₃ and P ₄ in the hose sections 131 , 151 and fluid passageway 141 respectively, are equal to the initial pressure Po _.

The piston 111 of the hydraulic cylinder 110 is actionable from the outside. Prior to any force acting on the piston 111 , the piston 111 is in an extended position in which it extends to its maximum extent out from the main body 112 of the hydraulic cylinder 110.

Since the force generator valve 142 and the solenoid valve 143 are in their default positions i.e. unactuated states, the first and second flow channels 1413, 1414 of the fluid passageway 141 of the control block 140 are blocked and fluid cannot pass through the first or second flow channels 1413, 1414.

When a forced is applied to the hydraulic cylinders 110, causing compression of the pistons 111 , oil 180 is forced out of the cylinders 112 into the hose sections 131 (see Fig. 9b) increasing the pressure Pi in the hose section 131 i.e. Pi > Po.

With continued compression of the pistons 111 , the oil 180 is forced through the manifold 120, through the hose section 151 and into the control block 140 via the hose section 151 (see Fig. 9c). The pressures P ₂ and P ₃ in the hose section 151 and in the portion of the fluid passageway 141 are increased i.e. P ₂ > Po and P ₃ > Po.

Since the first and second flow channels 1413, 1414 are in a closed state, the continued ingress of oil 180 into the control block 140 by the continued compression of the pistons 111 will result in the pressure P3 increasing, resulting in the oil 180 applying a pressure force on the force generator valve 142.

When the force acting on the force generator valve 142 by the oil 180 exceeds the predetermined/default value P _D of the force required to actuate the force generator valve 142, i.e. P ₃ > PD, the force generator valve 142 will be actuated to open the first flow channel 1413.

Once the first flow channel 1413 is opened, oil 180 will flow into the accumulator 160 and build up behind the movable piston 163 of the accumulator i.e. P ₃ > PD and P ₄ > Po (see Fig. 9d).

As more oil 180 enters the accumulator 160, the volume of the first chamber 161 increases which results in a decrease in the volume of the second chamber 162, compressing the nitrogen stored in the second chamber 162 (see Fig. 9e). On completion of the compression stroke of the pistons 111 of the gas springs 1 10, there is a reduction in the pressure force acting on the force generator valve 142, which causes it to return to its default state and close off the first flow channel 1413 i.e. Po < P3 < P _D (see Fig. 9f).

Since there is no returning force in the cylinders 112 or the linear actuator assembly 100 from the cylinders 112 up to the control block 140, the pistons 111 will not return towards or to an extended position if the load upon them is reduced or removed.

The return of the pistons 111 towards/to an extended position will now be described with reference to Figs. 10a to 10d.

After the load acting on the pistons 111 is removed, an electrical signal is sent to the solenoid valve 143, to open the valve 143.

Opening the solenoid valve 143, results in the opening of the second flow channel 1414 of the fluid passageway 141 (see Fig. 11a).

Once the second flow channel 1414 is opened, the compressive force of the oil 180 acting on the movable piston 163 in the accumulator is reduced to below the expansive force of the compressed nitrogen.

As the nitrogen expands, resulting in expansion of the second chamber 162 thus moving the pitons 163 to reduce the volume of the first chamber, oil 180 is forced out of the accumulator 160 and into the cylinders 112 (see Fig. 10b).

As oil 180 returns to the cylinders 112, the pistons 111 move towards their extended position (see Fig. 10c).

Once the pistons 111 are back in their extended positions, the solenoid valve is closed and the system is ready for another compression stroke (see Fig. 10d).

Referring to figs. 11a and 11 b, an embodiment of a metal press 10 having a press tool 12 incorporating a linear actuator assembly in accordance with the invention is shown.

The linear actuator system of the metal press 10 is shown with a linear actuator assembly 100 in accordance with the first embodiment.

For clarity, only the top plate 13, bottom plate 14, and trust plate 15 are shown in addition to the linear actuator assembly 100. The other components of the press tool 12, and their arrangement, are similar to those in press tools in the art. The linear actuator system has a first unit 50 arranged to be mounted on a section of the press tool 12, a second unit 60 configured to be positioned at a distance from the press tool, and a coupling arrangement 70 for coupling arrangement configured to connect the first unit to the second unit.

The coupling arrangement corresponds to the manifold-control block coupling arrangement as previously described in relation to the linear actuator assembly 100.

The first unit 50 includes the plurality of hydraulic cylinders, the manifold block, and the cylinder-manifold coupling arrangement of the linear actuator assembly 100. The first unit is incorporated into the press tool.

The second unit 70 includes a control block and accumulator components of the linear actuator assembly 100.

In the linear actuator system of the invention, the control block and accumulator components are not housed in or located with the press tool. This is advantageous in that the press tool does not needed to be designed in such a way to accommodate these components and as such the overall footprint of the press tool will be smaller than one which incorporates a control block and accumulator therein.

There are numerous advantages of the linear actuator assembly of the present invention over systems know in the art.

For example, the linear actuator assembly does not require an air source.

In addition, due to the nature of the accumulator arrangement, cylinders of a smaller dimension can be used than current cylinders in the art for the same pressing applications.

The linear actuator assembly in accordance with the invention allows for the spring pressure of the hydraulic cylinders to be adjusted by adjusting the pressure valve of the control module.

The quick disconnect used with the linear actuator assembly of the invention mean that the assembly provides a modular system which can be adapted to fit tool design.

The linear actuator assembly in accordance with the invention allows for the accumulator to be positioned outside the tool, either on the bolster or outside the press. This is advantageous as it reduces the foot print or floor space required for the tool. Due to the fact that that the accumulator can be easily disconnected from the other components of the linear actuator assembly, the accumulator can be disconnected after each run meaning that it can say by the press rather than be moved with the tool.

In addition, the accumulator can be used for multiple tools, thus not restricting the use of the linear actuator assembly by having to have an accumulator for each tool.

The quick disconnects allow for disconnecting any part of the modular system provided by the linear actuator assembly of the invention and then reconnecting without the need to recharge with oil or nitrogen.

The arrangement of the linear actuator assembly of the invention allows the design of the tool to be a lot more compact or easier as the larger components (accumulator/control block) can be designed to be positioned outside the main tool.

While the embodiment of the linear actuator assemblies in accordance with the invention have been shown and described having four hydraulic cylinders, it would be understood that a different number of hydraulic cylinders may be utilized depending on the size and shape of the workpiece in use.

While the hose sections 131 , 231 have been described or shown as being connected to a respective hydraulic cylinders 110, 210 and the manifold block 120, 220 by a quick disconnect, it would be understood that a threaded or flanged connection may instead be used at one or both ends of the hose section 131 , 231 as known in the art.

While the accumulator 160, 260 has been described as being connected to the control block 140 by a quick disconnect, it would be understood that a threaded or flanged connection may instead be used to connect the accumulator 160, 260 to the control block 140.

While the compressed gas accumulator forming part of the invention has been described as a piston accumulator, it would be understood that other forms of compressed gas accumulators may be used instead.