A PISTON AND CYLINDER SYSTEM

Field of the Invention

THIS INVENTION relates to a piston and cylinder system. In particular, the invention relates to a method of driving a piston to displace within a cylinder, to a piston and cylinder system and to a heat transfer arrangement.

Summary of the Invention

According to a first aspect of the invention, there is provided a method of driving a piston to displace within a cylinder, the method including providing at least one piston and cylinder assembly defining a piston positioned within a cylinder for displacement internally along the cylinder, a chamber on one side of the piston within the cylinder and another chamber on an opposed side of the piston within the cylinder, providing a heat transfer arrangement defining two heat transfer chambers and heat transfer means arranged selectively to transfer heat between the heat transfer chambers, connecting one of the heat transfer chambers in flow communication with one of the chambers defined by the piston and cylinder assembly to define a closed volume, connecting the other of the heat transfer chambers in flow communication with the other of the chambers defined by the piston and cylinder assembly to define another closed volume and causing the heat transfer means selectively to transfer heat between the heat transfer chambers thereby to cause the piston selectively to displace in opposed directions internally along the cylinder.

Providing a heat transfer arrangement defining two heat transfer chambers and heat transfer means arranged selectively to transfer heat between the heat transfer chambers may include providing a heat transfer arrangement in which the heat transfer means is in the form of a Peltier heat transfer device arranged selectively to transfer heat between the two heat transfer chambers.

The method may further include loading the piston in one direction with a load and pressurizing one of the closed volumes to compensate for the load.

Causing the heat transfer means selectively to transfer heat between the heat transfer chambers thereby to cause the piston selectively to displace in opposed directions internally along the cylinder may include selectively causing a fluid to circulate within each of the heat transfer chambers.

Selectively causing a fluid to circulate within each of the heat transfer chambers may include guiding the fluid from one region of each heat transfer chamber to an opposed region of each heat transfer chamber.

Guiding the fluid from one region of each heat transfer chamber to an opposed region of each heat transfer chamber may include guiding the fluid through at least one conduit extending in flow communication between the one region and the opposed region of each heat transfer chamber.

Guiding the fluid through at least one conduit extending in flow communication between the one region and the opposed region of each heat transfer chamber may include selectively cooling the conduits.

Selectively causing a fluid to circulate within each of the heat transfer chambers may include causing the fluid to pass across a heat sink within each of the heat transfer chambers, the heat sinks being in heat flow communication with the heat transfer means.

The method may further include charging each of the closed volumes with a fluid in the form of Nitrogen.

According to another aspect of the invention, there is provided a piston and cylinder system including at least one piston and cylinder assembly defining a piston positioned within a cylinder for displacement internally along the cylinder, a chamber on one side of the piston within the cylinder and another chamber on an opposed side of the piston within the cylinder, a heat transfer arrangement defining two heat transfer chambers and heat transfer means arranged selectively to transfer heat between the heat transfer chambers, one of the heat transfer chambers being in flow communication with one of the chambers defined by the piston and cylinder assembly to define a closed volume and the other of the heat transfer chambers being in flow communication with the other of the chambers defined by the piston and cylinder assembly to define another closed volume and control means for causing the heat transfer means selectively to transfer heat between the heat transfer chambers thereby to cause the piston selectively to displace in opposed directions internally along the cylinder.

The heat transfer means may be in the form of a Peltier heat transfer device arranged selectively to transfer heat between the two heat transfer chambers.

The piston may be under a load in one direction, one of the closed volumes then being pressurized to compensate for the load.

The piston and cylinder system may further include circulation means for selectively causing a fluid to circulate within each of the heat transfer chambers.

The piston and cylinder system may further include guide means for guiding the fluid from one region of each heat transfer chamber to an opposed region of each heat transfer chamber.

The guide means may include at least one conduit extending in flow communication between the one region and the opposed region of each heat transfer chamber.

The piston and cylinder system may further include cooling means for selectively cooling the conduits.

The piston and cylinder system may further include a heat sink within each of the heat transfer chambers, the heat sinks being in heat flow communication with the heat transfer means.

The closed volumes may be charged with Nitrogen.

According to a further aspect of the invention, there is provided a heat transfer arrangement including a body, two heat transfer chambers defined by the body, heat transfer means positioned on the body operatively between the two heat transfer chambers for selectively transferring heat between the heat transfer chambers, connection means for connecting one of the heat transfer chambers in flow communication with a chamber defined by a piston and cylinder assembly so as to define a closed volume, connection means for connecting the other of the heat transfer chambers in flow communication with another chamber defined by the piston and cylinder assembly so as to define another closed volume and control means for causing the heat transfer means selectively to transfer heat between the heat transfer chambers, in use.

The heat transfer means may be in the form of a Peltier heat transfer device for selectively transferring heat between the two heat transfer chambers.

The heat transfer arrangement may further include circulation means for selectively causing a fluid to circulate within each of the heat transfer chambers.

The circulation means may include an electrically operable fan positioned within each of the heat transfer chambers.

The heat transfer arrangement may further include guide means for guiding the fluid from one region of each heat transfer chamber to an opposed region of each heat transfer chamber.

The guide means may include at least one conduit extending in flow communication between the one region and the opposed region of each heat transfer chamber.

The heat transfer arrangement may further include cooling means for selectively cooling the conduits.

The cooling means may include an electrically operable fan operable selectively to cool the conduits.

The heat transfer arrangement may further include a heat sink within each of the heat transfer chambers, the heat sinks being in heat flow communication with the heat transfer means.

A Peltier heat transfer device transfers heat from one side thereof to the other side, however, more heat is generated on the hot side than that which was removed on the cold side. Thus, for example, with a cold side wattage of 32 watt and a power input of 44 watt, the resultant hot side wattage is 76 watt. This leads to the advantage that there is a higher pressure differential between the cold and hot sides which permits higher acceleration of a load which is displaced thereby.

Description of Embodiments of the Invention

Embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Figure 1 shows a schematic diagram showing an embodiment of a piston and cylinder system in accordance with an aspect of the invention;

Figure IA corresponds with Figure 1 of the drawings, and shows a piston being displaced in a cylinder in response to heat transfer between one heat transfer chamber and another heat transfer chamber of the piston and cylinder system;

Figure IB corresponds with Figures 1 and IA of the drawings, and shows the piston being displaced in the cylinder in an opposed direction in response to heat transfer between the other heat transfer chamber and the one heat transfer chamber of the piston and cylinder system;

Figure 2 shows a schematic diagram showing another embodiment of a piston and cylinder system in accordance with the invention;

Figure 3 shows a schematic three dimensional view of an embodiment of a heat transfer arrangement in accordance with another aspect of the invention; and

Figure 4 shows a schematic diagram showing the working of the heat transfer arrangement shown in Figure 3.

Referring to Figures 1, IA and IB of the drawings, a piston and cylinder system in accordance with an embodiment of the invention, is generally indicated by reference numeral 10.

The piston and cylinder system 10 includes at least one piston and cylinder assembly, generally indicated by reference numeral 12. The piston and cylinder assembly defines a piston 14 positioned within a cylinder 16 for displacement internally along the cylinder 16. A chamber 18 is defined on one side of the piston 14 within the cylinder 16 and another chamber 20 is defined on an opposed side of the piston 14 within the cylinder 16.

The piston and cylinder system 10 further includes a heat transfer arrangement, generally indicated by reference numeral 30. The heat transfer arrangement 30 defines two heat transfer chambers 32, 34 and heat transfer means, generally indicated by reference numeral 36, arranged selectively to transfer heat between the heat transfer chambers 32, 34. Typically, the heat transfer means 36 is in the form of a Peltier heat transfer device, or element.

One of the heat transfer chambers, namely the heat transfer chamber 32, is in flow communication with one of the chambers, namely the chamber 18, defined by the piston and cylinder assembly 12. A closed volume 13 is defined by the chamber 18 and the heat transfer chamber 32. The other of the heat transfer chambers, namely the heat transfer chamber 34 is in flow communication with the other of the chambers, namely the chamber 20, defined by the piston and cylinder assembly 12. Another closed volume 15 is defined by the chamber 20 and the heat transfer chamber 34.

Control means, for causing the heat transfer means 36 selectively to transfer heat between the heat transfer chambers 32, 34, is generally indicated at 40. When heat is selectively transferred between the heat transfer chambers 32, 34, the piston 14 is selectively caused to displace in opposed directions internally along the cylinder 16. Accordingly, when heat is transferred from the heat transfer chamber 32 to the heat transfer chamber 34 as indicated by the arrow A, the piston 14 is caused to displace in the direction of the arrow Al . When heat is transferred from the heat transfer chamber 34 to the heat transfer chamber 32 as indicated by the arrow B, the piston 14 is caused to displace in the direction of the arrow B 1.

In one embodiment, the piston 14 is under a load, as indicated by arrow C, in one direction. In such a case, one of the closed volumes, in this case the closed volume 15 is pressurized to compensate for the load C. Accordingly, a pressure differential δP exists between the closed volumes 13, 15 which compensates for a force exerted on the piston

14 by the load C.

Typically, the closed volumes 13, 15 are charged with a fluid, such as, air, or an inert gas, for example, such as Nitrogen, or the like, for example.

Referring now to Figure 2 of the drawings, in which like reference numerals have been used to designate similar parts, or features, unless otherwise stated, another embodiment of a piston and cylinder system in accordance with the invention, is generally indicated by reference numeral 110.

The piston and cylinder system 110 includes a plurality, in this case two, piston and cylinder assemblies, generally indicated by reference numerals 111, 112. The piston and cylinder assemblies 111, 112 define pistons 114, 114 positioned within cylinders 116, 116 for displacement internally along the cylinders 116, 116. A chamber 118 is defined on one side of each of the pistons 114, 114 within the cylinders 116, 116 and another chamber 120 is defined on an opposed side of each of the pistons 114, 114 within the cylinders 116, 116.

The piston and cylinder system 110 further includes a heat transfer arrangement, generally indicated by reference numeral 130. The heat transfer arrangement 130 defines two heat transfer chambers 132, 134 and heat transfer means, generally indicated by reference numeral 136, arranged selectively to transfer heat between the heat transfer chambers 132, 134. Typically, the heat transfer means 136 is in the form of a Peltier heat transfer device, or element. It has been found that a 33 Watt Peltier heat transfer device can be used where the piston and cylinder system 110 is used to actuate an average garage door, or the like, for example.

The heat transfer chamber 132 is in flow communication with the chambers 120,

120. A closed volume 113 is defined by the chambers 120, 120 and the heat transfer chamber 132. The heat transfer chamber 134 is in flow communication with the chambers 118, 118 to define another closed volume 115 defined by the chambers 118,

118 and the heat transfer chamber 134.

With reference to Figures 3 and 4 of the drawings, in which like reference numerals have been used to designate similar parts, or features, unless otherwise stated, further aspects of the piston and cylinder system 110 will now be described.

The heat transfer arrangement 130 includes a body, generally indicated by reference numeral 210. The body 210 includes a polycarbonate plate 212 sandwiched between two polycarbonate housings 214, 216. The heat transfer chambers 132, 134 are defined by the body 210, between the polycarbonate plate 212 and the polycarbonate housings 214, 216. The heat transfer means 136 is positioned on the body 210 operatively between the two heat transfer chambers 132, 134 for selectively transferring heat between the heat transfer chambers 132, 134. The heat transfer arrangement includes connection means, generally indicated at 135, 137 in Figure 2 of the drawings, for connecting the heat transfer chambers 132, 134 in flow communication with the chambers 118, 120 defined by the piston and cylinder assemblies 111, 112. The connection means 135, 137 can be in the form of internally screw-threaded apertures, or the like, for example, so as to enable conduits 140, 142 to be screw-threadedly secured with the internally screw-threaded apertures so as to connect the heat transfer chambers 132, 134 in flow communication with the chambers 120, 118 respectively, by means of the conduits 140, 142.

The heat transfer arrangement 130 further includes circulation means, generally indicated by reference numerals 150, 150 for selectively causing a fluid to circulate within each of the heat transfer chambers 132, 134. The circulation means 150 includes an electrically operable fan 152 positioned within each of the heat transfer chambers 132

134.

The heat transfer arrangement 130 further includes guide means, generally indicated by reference numeral 154, for guiding the fluid from one region 132.1, 134.1 of each heat transfer chamber 132, 134 to an opposed region, 132.2, 134.2 of each heat transfer chamber 132, 134, as indicated by arrows D. The guide means 154 includes at

least one conduit, in this case six conduits 156, extending in flow communication between the one region 132.1, 134.1 and the opposed region 132.2, 134.2 of each heat transfer chamber 132, 134. Only two of the conduits 156 are shown in Figure 4 for the sake of clarity. Typically, the conduits 156 extend between six ports 158 positioned at an end of the body 210 and six ports 158 positioned at an opposed end of the body 210, as can best be seen with reference to Figure 3 of the drawings. The conduits 156 can be of any appropriate material, such as, composite aluminum and plastic pipe having a diameter of 16 mm, or the like, for example.

The heat transfer arrangement 130 further includes a heat sink within each of the heat transfer chambers 132, 134. The heat sinks 160, 160 are in heat flow communication with the heat transfer means 136. The heat sinks 160, 160 can be of any appropriate heat conductive material, such as Aluminium, or the like, for example. Heat pipe heat sinks can be used in some cases.

Returning now to Figure 2 of the drawings, the piston and cylinder system 110 can include cooling means, generally indicated in dashed lines by reference numeral 162, for selectively cooling the conduits 156, as indicated by dashed arrows E. It will be appreciated that the conduits 156 are not shown in Figure 2 for the sake of clarity. In one embodiment, the cooling means 162 includes an electrically operable fan 164 operable selectively to cool the conduits 156. A shroud 166 can be provided to assist convection cooling of the conduits 156 by the fan 164.

Control means, generally indicated by reference numeral 174, for controlling the heat transfer means 136 selectively to transfer heat between the heat transfer chambers 132, 134 is provided.

fbe control means 174 can include any appropriate controller 176, such as a PR

59 fully programmable PlD controller available from Supercool ^IM , or the hie, for example, with appropriate programming Typical Iy, the controller 176 ih connected Io a computer 17S by means of a .serial cable 180, or the hie, for example In the case where

the heat transfer means 136 is in the form of a Peltier element, the Peltier element is controlled with the aid of a temperature sensor 182 in one, or both, of the heat transfer chambers 132, 134. By means of a temperature reading by the temperature sensor, or sensors 182, electrical power supplied to the Peltier element and a speed of the fans 150, 150 can be controlled thereby to regulate the pressure within the closed volumes 1 13, 1 15.

λn appropriate connector 184, such as, a panel-mount mini weather tight circular cable malc _' 'female 4 pin connector, or the like, for example, is sealingly secured on the body 210 for operatively connecting the peltier element and the fans 150, 150 to the controller 176,

λn appropriate connector 18(x such as, a panel-mount mini weather tight circular cable male-female 3 pin connector, or the like, for example, is sealingly secured on the body 210 for operative Iy connecting the temperature sensor, or sensors 1 S2, to the controller 176,

In use, the piston and cylinder assemblies 111, 112 and the heat transfer arrangement 130 are provided. The one of the heat transfer chambers, namely the chamber 132, is connected in flow communication with the chambers 120, 120 defined by the piston and cylinder assemblies 111, 112 to define the closed volume 113. This is typically achieved by means of the conduit 140 and a T-piece 141 extending between the chambers 120, 120 and the connection means 135. Similarly, the other of the heat transfer chambers, namely the chamber 134, is connected in flow communication with the chambers 118, 118 defined by the piston and cylinder assemblies 111, 112 to define the closed volume 115. This is typically achieved by means of the conduit 142 and a T- piece 143 extending between the chambers 118, 118 and the connection means 137.

The method can include loading the piston in one direction with a load C and pressurizing a corresponding one of the closed volumes 113, 115, in this case the closed volume 113, to compensate for the load C. Where the piston and cylinder system 110 is

to be used as an actuator for selectively opening and closing a garage door, or the like, for example, the load C corresponds to the weight of the garage door. By pressurizing the closed volume 113, the weight of the garage door can be compensated for in a pre-load fashion. By then causing the heat transfer means 136 selectively to transfer heat between the heat transfer chambers 132, 134, as indicated by arrows A, B, the pistons 114, 114 are caused selectively to displace internally along the cylinders 116, 116 in opposed directions, as indicated by arrows Al, Bl. Accordingly, when the heat transfer means 136 is caused to transfer heat from the heat transfer chamber 134 to the heat transfer chamber 132 in the direction of arrow B, the pistons 114 are caused to displace in the direction of arrows Bl, Bl, so as to open a garage door from a closed position, for example. When the heat transfer means 136 is caused to transfer heat from the heat transfer chamber 132 to the heat transfer chamber 134 in the direction of arrow A, the pistons 114, 114 are caused to displace in the direction of arrows Al, Al, so as to close the garage door from an open position, for example.

When the heat transfer means 136 is selectively caused to transfer heat between the heat transfer chambers 132, 134, fluid in the closed volumes 113, 115, is caused to circulate within each of the heat transfer chambers. It will be appreciated that this enhances heat transfer between the chambers 132, 134. As can best be seen with reference to Figure 4 of the drawings, the fluid is caused to circulate in the directions of arrows D, namely from the regions 132.1, 134.1, guided through the conduits 156, to the opposed regions 132.2, 134.2 and from the opposed regions 132.2, 134.2 along the chambers 132, 134 back to the regions 132.1, 134.1.

As the fluid circulates from the opposed regions 132.2, 134.2 along the chambers

132, 134 back to the regions 132.1, 134.1, the fluid passes across the heat sinks 160, 160 within each of the heat transfer chambers 132, 134. The heat sinks 160, 160 are in heat flow communication with the heat transfer means 136. Accordingly, the heat sinks 160, 160 enhance heat transfer between the chambers 132, 134 as the fluid passes across the heat sinks 160, 160.

It will be appreciated that the conduits 156 associated with a one of the heat transfer chambers 132, 134 to which heat was transferred from the other of the heat transfer chambers 132, 134 can absorb heat from the fluid and become heated. If it is then desired to transfer heat back from the other of the heat transfer chambers 132, 134 to the one of the heat transfer chambers 132, 134, the heated conduits 156 can retard heat transfer back to the one of the heat transfer chambers 132, 134. To this end, the conduits 156 are convection cooled after heat has been transferred between the heat transfer chambers 132, 134 by the fan 164 in cooperation with the shroud 162.

A valve 1 70 and a pressure gauge 172 can be provided along each of the conduits

1-10. 142. By moans of the valves 170, 170 the flow and pressure of the fluid from the chambers 132, 134 to the piston and cylinder assemblies 1 1 1 , 112 can be controlled thereby to control the speed of travel of the pistons 1 14, 1 14 in the cylinders 1 Id, 1 16 for example. The valves 170, 170 can be closed initially while Peltier heating and cooling between the heat transfer chambers 132, 134 takes place, thereby to vary a pressure differential between the chambers 132, 134 Tbe valves 170. 1 ^~ Q can then be opened to cause the piston and cylinder assemblies 1 1 1 , 112 to do work, such as, to lift a weight, to lift a garage door, or the like, for example

The valves 170. 170 can be used to interrupt displacement of the pistons 114, 114 m the cylinders 1 16, 1 16 when desired, for example In the event that the valves 170, 170 are closed, the pistons 1 14, 1 14 will settle to where the pressure differential across {be pistons 1 14, 1 14 is in equilibrium with the load C.

The valves 170, 170 can form part of a safety system of the piston and cylinder system 110. For example, the valves 170, 170 can be operatively connected to a sensor, or the like, for example, which detects interference with movement of a garage door, or the like, for example, while the garage door is being lifted by the piston an J cylinder assemblies 111, 1 12, thereby to interrupt drive to the pistons 114. 1 14.

The pressure gauges 172, 172 can be used to determine the pressure of the closed volumes 113, 115. In addition, the pressure gauges 172, 172 can be used to obtain a correct pressure differentia] between the closed volumes 113, 1 15 where the pistons 114, 114 are under a load C,

The Applicant believes a piston and cylinder system in accordance with the inven H on lias several advantages when compared with conventional piston and cylinder systems of which the Applicant is aware.

Firstly, the operating parts of the piston and cylinder system in accordance with the invention are relatively particle and water contamination resistant. Secondly, the system can readily be applied to conventional rod and rodless piston and cylinder assemblies which are readily available. Thirdly, in the case of a load on the pistons, the initial pressure differential stays relatively constant irrespective of environmental temperature variations since the closed volumes are typically set up initially at the same room temperature. Accordingly, pressure adjustment to cater for variation in environmental temperature changes is typically not required.

Fourthly, the piston and cylinder system in accordance with the invention has relatively few moving parts. Fifthly, power consumption is typically less than in the case of conventional electrical motors. Sixthly, the piston and cylinder system in accordance with the invention can be used advantageously in a variety of different applications, such as, to open and close garage doors, entrance doors, as actuators in the field of robotics, and the like, for example. Seventhly, the piston and cylinder system in accordance with the invention can operate from a relatively low, and relatively safe, power supply, such as, a 12 Volt power supply, or a 17 volt power supply, or the like, for example.