WO2007091952A1

WO2007091952A1 - A weighing valve device

Info

Publication number: WO2007091952A1
Application number: PCT/SE2007/000112
Authority: WO
Inventors: Fred Emilsson
Original assignee: Faiveley Transport Nordic Ab
Priority date: 2006-02-09
Filing date: 2007-02-07
Publication date: 2007-08-16
Also published as: SE0600280L; EP1981744A1; SE529603C2

Abstract

A weighing valve device comprises a housing (101) with a cover (104) , an axially movable piston (102) in a bore in the housing (101) and an enclosed body (103) of plastically deformable material in the piston (102). A differential piston (105-107) with a smaller diameter piston part (106) is in contact with the body (103) and with a larger diameter piston part in the form of a diaphragm (105) clamped between the housing (101) and the cover (104) and backed by a disc (107). A valve with an axially movable, spring-biassed valve member (110) is in contact with the diaphragm. A compressed air pressure acting on the diaphragm (105) and governed by the valve is adapted to counteract a mechanical force on the piston (102). The smaller diameter part (106) of the differential piston (105-107) rests against the disc (107) at its center. The diaphragm (105) and the disc (107) are provided at their centres with a through passage (111) for venting of compressed-air. The valve member (110) is arranged over the through passage (111). The smaller diameter piston part (106) is guided by a guide sleeve (108') in a guide block (108) above the enclosed body (103).

Description

A WEIGHING VALVE DEVICE

Technical Field The present invention relates to a weighing valve device, comprising a housing with a cover, an axially movable piston in a bore in the housing, an enclosed body of plastically deformable material in the piston, a differential piston with a smaller diameter piston part in contact with the body and with a larger diameter piston part in the form of a diaphragm clamped between the housing and the cover and backed by a disc, and a valve with an axially movable, spring-biassed valve member in contact with the diaphragm, wherein a compressed air pressure acting on the diaphragm and governed by the valve is adapted to counteract a mechanical force- on the piston. Background of the Invention

A weighing valve device of the kind referred to above is intended for use on a rail vehicle for governing servomotors in systems for regulating brake forces to suit loads on the vehicle. Differently speaking such a device is intended to submit an air pressure depending on the load on the vehicle to be used to adapt the brake force to the load on the vehicle.

Such a weighing valve device in current use is shown in GB-B-I 314 286 (and also in the present document as a Fig 1 embodiment) . A growing concern in the construction of rail vehicles is the space available for devices of this nature .

An important object of the present invention is accordingly to reduce the external dimensions of the device without in any way to impair its performance. It has further appeared that an extensively used weighing valve device of the current design in certain cases may experience internal wear, leading to a kind of , valve leakage and an increased air consumption. Another object of the invention is accordingly to obtain a weighing valve device, which does not exhibit such an increased air consumption even after a long service period.

The Invention This is according to the invention attained in that the smaller diameter part of the differential piston rests against the disc at its center, the diaphragm and the disc at their centres are provided with a through passage for venting of compressed air, the valve member is arranged over the through passage, and the smaller diameter piston part is guided by a guide sleeve in a guide block above the enclosed body. The weighing valve device according to GB-B-I 314 286 has a valve member, which is positioned offset in relation to the center of the disc and the diaphragm, whereas the valve member in the device according to the present invention is centrally located. A weighing valve device of the same general kind as defined above under the heading

"Technical Field" and with a centrally located valve member is shown in GB-B-I 296 311. However, this prior art device does not have the combination of the characterizing features defined above. Further features of the inventive device appear from the dependent claims .

Brief Description of the Drawings

The invention will be described in further detail below under reference to the accompanying drawings, in which Fig 1 is a vertical cross section through a known weighing valve device,

Fig 2 is a corresponding section through a weighing, valve device according to the invention, and ' Figs 3 and 4 are sections through portions of alternative embodiments of the weighing valve device of Fig 2.

Detailed Description of a Preferred Embodiment A known weighing valve device, primarily for a rail vehicle, is shown in Fig 1. It comprises a housing 1 having a cylindrical bore accomodating an axially movable piston 2. In a central bore of the piston 2 there is a body 3 of plastically deformable material, for example polyethylene or silicon rubber. The housing 1 is provided with a' cover 4, the margin of a flexible diaphragm 5 being clamped between the housing 1 and the cover 4. The diaphragm 5 forms a part of a differential piston consisting of a smaller diameter piston part 6 rigidly connected to a disc 7, which may be attached to the diaphragm 5 or not. The diaphragm 5 acts as a larger diameter part of the differential piston.

The smaller diameter piston part 6 penetrates into the plastically deformable body 3 through a force- transmitting and guiding block 8 above the body 3 in the bore of the piston 2. The smaller diameter piston part 6 is guided by a guide sleeve I' in the housing 1.

The space between the diaphragm 5 and the cover 4 is supplied from a suitable source (not shown) with compressed air, which enters the device through a separate inlet A" and further to an inlet valve housing 9 connected to the cover 4 and containing a valve member 10. The valve member 10 is in spring biassed engagement with the diaphragm 5 over a passage 11 extending through the diaphragm 5 and the disc 7. The space below the diaphragm 5 and the disc 7 communicates with the exterior through an escape passage 12, preferably provided with a nipple 12" at the outlet for preventing the intrusion of dirt and the like. A resilient O-ring 13 is mounted on the valve member 10 for engagement with an internal shoulder in the valve housing 9. A compression spring 14 is arranged between the valve member 10 and a sealed cap 15 for the valve housing 9. An outlet 4" is adapted to connect the space between the cover 4 and the diaphragm 5 through a hose (not shown) to a servo-motor or the like (not shown) , which the weighing valve device is intended to control .

A sealing ring 16 and a backing ring 17 of low- friction lubrication-free sealing material are provided between the body 3 and the guiding block 8 , whereas a guiding sleeve 18 of for example Delrin^® or Teflon^® is arranged between the piston 2 and the housing 1. A gland 19 is provided at the lower end of the housing 1 to provide for tightness and to loosely hold the piston 2.

The shown and described weighing valve device is adapted to be subjected to compression and to transmit force depending on the weight of the vehicle, on which it is mounted in a way known to the person skilled in the art. The device contacts one vehicle part with a lower end 20 of the piston 2 and another vehicle part with a flange 21 of the housing 1 externally of the cover 4.

The weighing valve device operates in the following way: The pressure in the material of the body 3 will urge the smaller diameter piston part 6 upwards. However, this upwardly directed force will be counteracted by a downwardly directed force on the disc 7 caused by the pressure of the air above the diaphragm 5. If the force transmitted is increased, the piston part 6 and the disc 7 will move upwards thus causing the the diaphragm 5 to raise the valve member 10, and consequently the inlet valve opens to establish a connection between the interior of the inlet valve housing 9 and the space above the diaphragm 5. Compressed air now enters this space, causing a downward movement of the latter, until the inlet valve is closed again. As a result, the air pressure above the diaphragm 5 has been increased in proportion to the increase in the transmitted force, and this air pressure is transmitted through the outlet 4" to be used as a signal related to the magnitude of the transmitted force, or in other words to the weight of the vehicle . If the transmitted force is decreased, the piston part 6 will move downwards. This will cause a gap between the valve member 10 and the diaphragm 5. The space above the diaphragm 5 is thus vented through the passages 11 and 12. Consequently, as the inlet valve remains closed, the pressure of the air above the diaphragm 5 is decreased, and this permits an upward movement of the differential piston, until the diaphragm again contacts the valve member 10 and thus stops any further escape of air.

As a result, the air pressure above the diaphragm 5 will again correspond to the magnitude of the force being transmitted by the device.

Fig 2 shows a weighing valve device according to the invention. Corresponding parts are provided with the same numerals in Fig 2 as in Fig 1 with the addition of 100, which for example means that the housing in the Fig 1 embodiment bears the number 1 and in the Fig 2 embodiment 101.

It is not necessary to give a full description of the Fig 2 embodiment and its function, but reference is made to the previous description with the above remark about the numbering in mind.

The main object of the invention is to provide a weighing valve device with smaller external dimensions but _,5 with^" the same function and capabilities as the known one shown in Fig 1. This has been accomplished in a number of ways, as will appear.

The overall height of the weighing valve device has in principle been cut down to half (for example from about 0 150 mm to 80 mm, or less as shown in Figs 3 and 4) . An important change is that the length of the piston 102 has been greatly reduced. The sleeve 18 has been replaced by two guiding rings 118 of polymeric material with improved guiding properties, and the diameter of the piston 102 has 5 been increased, which together means that the piston 102 is appropriately guided without any jamming effect. Also the height or axial length of the block 108 has been decreased.

The smaller diameter piston part 106 is no longer rigidly connected to the disc 107 but only bears against 0 it, whereas the diaphragm 105 is attached to the disc 107 by a number of rubber rivets. Further, the smaller diameter piston part 106 is guided by a guide sleeve 108 " connected to the guiding block 108 and moves freely in the housing 101. 5 By the measures in the preceding paragraph a potential drawback with the known device of Fig 1 can be obviated. In that design a possible wear of the guiding for the piston 2 could lead to a slight pivoting movement of the disc 7 at operation, which could result in an 0 inadvertent opening of the valve member 10 and unnecessary air consumption.

The valve member 110 is now centrally located directly in the cover 104 in line with the smaller diameter piston part 106, which means that all forces are solely axial. The valve member 110 also has a reduced axial dimension.

The fact that the piston part 106 is not connected to the disc 107 means that the passage 111 can be in axial line therewith and of course with the central valve member 110.

A further design change of importance both for the height and width (diameter) of the weighing valve device has regard to the cover design. In the known device the cover 4 is placed with a brim over the top of the device, whereas a housing flange 21 outside thereof serves for force-transmittingly connecting the device to the vehicle.

In the device according to the invention the cover 104 (practically without any brim) with reduced diameter is placed flatly on top of the housing 101, and a ring-shaped upper surface 104A serves for force-transmittingly connecting the device to the vehicle. With the diameter of the diaphragm 105 left practically unchanged, the outside width dimension of the weighing valve device can in principle.be reduced to half, namely from about 200 mm for the prior weighing valve device (including the flanges 21) to about 110 mm.

Another design change carried out is to allow the passage 112 to go down in the housing 101 and open within the gland 119, which is provided with a vent opening 119' at an appropriate location not in line with the passage 112. In this way there is no need for a nipple 12"^*.

In the device as shown in Fig 2 the inlet 104' and the outlet 104" are placed in vertical protrusions on the cover 104. Alternatively and as illustrated in Figs 3 and 4, the inlet and the outlet can be differently arranged. In Fig 3 a horisontal position at the circumference of the cover is shown, whereas Fig 4 illustrates an inlet and/or outlet in the housing 101 in connection with the cover. By these alternative designs, the height of the weighing valve device can be further reduced and a greater flexibility with regard to the connection to the compressed air system in the vehicle be attained.

Modifications are possible within the scope of the appended claims .

Claims

1. A weighing valve device, comprising a housing (101) with a cover (104) , ah axially movable piston (102) in a bore in the housing (101) , an enclosed body (103) of plastically deformable material in the piston (102) , a differential piston (105-107) with a smaller diameter piston part (106) in contact with the body (103) and with a larger diameter piston part in the form of a diaphragm^' (105) clamped between the housing (101) and the cover (104) and backed by a disc (107) , and a valve with an axially movable, spring-biassed valve member (110) in contact with the diaphragm, wherein a compressed air pressure acting on the diaphragm (105) and governed by the valve is adapted to counteract .a mechanical force on the piston (102) , c h a r a ct e r i z e d in that the smaller diameter part (106) of the differential piston (105-107) rests against the disc (107) at its center, the diaphragm (105) and the disc (107) at their centres are provided with a through passage (111) for venting of compressed air, the valve member (110) is arranged over the through passage (111) , and the smaller diameter piston part (106) is guided by a guide sleeve (108') in a guide block (108) above the enclosed body (103) .

2. A device according to claim 1, wherein the cover (104) has the same external diameter as the housing (101) and is provided with an annular surface (104A) for its force-transmission support against a part of a vehicle, in which it is mounted.

3. A device according to claim 1, wherein a venting passage (112) extends through the housing (101) to the interior of a gland (119) where the piston (102) extends out of the housing (101) and the gland is provided with a venting hole (119") .

4. A device according to claim 1, wherein an inlet and an outlet for compressed air are arranged at the circumference of the cover (104) .

5. A device according to claim 1, wherein an inlet and an outlet for compressed air are arranged in the housing (101) and are connected to the cover (104) .