GB2191635A

GB2191635A - A manometer with a device for indicating insufficient pressure

Info

Publication number: GB2191635A
Application number: GB08713411A
Authority: GB
Inventors: Rodolfo Bitetti
Original assignee: Veglia Borletti SRL
Current assignee: Veglia Borletti SRL
Priority date: 1986-06-13
Filing date: 1987-06-09
Publication date: 1987-12-16
Also published as: IT8653527V0; GB8713411D0; FR2600160A3; ES1005854Y; ES1005854U; FR2600160B3; DE3719082A1; IT207802Z2

Description

SPECIFICATION A manometer with a device for indicating insufficient pressure The present invention relatesto a manometer, particularly for detecting the pressure of two independent pneumaticcircuits, provided with an electrical device for indicating insufficient pressure in one of the two circuits. Manometers are known comprising a resiliently deformable curved tubular element having an open, fixed end and a closed,free end which can be connected by the said fixed end to an hydraulic or pneumatic circuit so as to deform by an amount dependent on the pressure of the fluid in the circuit. Displacements of the said free end by the action of these deformations, are normally transformed by a suitable kinematicchain into rotation of an index positioned over a graduated scale which permits the pressure in the circuit to be read. Manometers of the type described are frequently employed on industrial vehicles provided with pneumatically actuated braking systems, and have the purpose of indicating to the driver the value of the pressure in the pneumatic circuit of the system itself.A possible anomaly in the pneumatic circuit the effect of which is to reduce the actuating pressure of the brakes is detected by the driver only by observing, when driving, the indication of an instrument positioned on the dashboard. Such anomaly may not be identified as soon as it occurs in thatthe dashboard generally includes a considerable number of other instruments, and there is at present no immediate and evident indication of an emergency condition. In the case in which the vehicle is a tractor vehicle the braking system is constituted bytwo independent pneumatic circuits which act respectively on the front axle and on the rear axle of the tractor itself; in this case there are two separate manometers on the dashboard, each indicating the pressure in the associated circuit. This obviously involves, on the part of the driver, the surveillance of both instruments and this is not particularly convenient in thatthe driver must closely checkthe position of the associated indices to be able to know if the pressure is above the pre-determined minimum value. The object of the present invention is that of providing a manometer which will be free from the disadvantages connected with known manometers specified above. Afurther object of the present invention is that of providing a manometerwhich permits the contemporaneous reading of pressure values in two independent pneumatic circuits. The said object is achieved with the present invention in that it relates to a manometer of the type comprising: at least one curved tubular metal element or plenum chamber having a fixed open end and another end which is free and closed, which can be connected by the said fixed end to an associated pneumatic circuit containing a fluid under pressure and resiliently deform by an amount dependent on the pressure of the said fluid; and a mechanism which transforms the displacements of the said free end caused by the deformations of the said plenum chamber into rotations of an associated index; characterised bythe factthat it includes electrical means operable to indicate a condition of insufficient pressure of the said fl uid. For a better understanding of the present invention a preferred embodiment is now described purely byway of non-limitative example and with reference to the attached drawings, in which: Figure 1 is a sectioned plan view of a manometer formed according to the principles of the present invention; and Figure 2 is a partially sectioned side view, on an enlarged scale, of a detail of the manometer shown in Figure 1. With particular reference to Figure 1, a manometer is generally indicated with the reference numeral 1 and comprises a circular support plate 2 on which are mounted two vertical ducts 3 and 4 which pass therethrough and two sections of different length of which project upwardly from the plate 2. From the closed upper ends of each of the ducts 3 and 4, in a direction orthogonal to the axes of the ducts 3 and 4 themselves, extend two tubular metal elements 5 and 6 having a substantiallyC-shape curve and an oblong section in a vertical sense, disposed in two superimposed horizontal planes, which hereinafter will be called "plenum chambers". The lower ends of the ducts 3 and 4, beneath the plate 2, have threaded spigots 7 and 8 operable to connectthe plenum chambers 5 and 6 with respective pneumatic circuits (notshown). At the closed opposite end, each of the two plenum chambers 5 and 6 is connected to a respective kinematic chain, generally indicated 9, which transforms the displacements of the ends thereof into rotation of an associated index 10 (shown in broken outline in the drawing) disposed over a suitable graduated scale (not illustrated). Asfarasthe plenum chamber6 is concerned,the kinematic chain 6, known per se, comprises a rod 11 rigidly connected at one end to the plenum chamber 6 itself and atthe other end carrying a pin 12 slidable in a slot 13formed longitudinally in an arm 14 of a lever 15. The lever 15, the fulcrum of which is constituted by a pin 16 fixed to the plate 2, has atthe end ofthe other arm 17 a circulartoothed sector 18 which meshes with corresponding teeth (not shown) of a spindle 19 fixed to the said index 10. In Figure 1 is shown only the kinematic chain relating to the plenum chamber 6; that associated with the other plenum chamber 5 is entirely similar. The only difference concerns the spindles 19 actuating the associated indices 10: the index 10, associated with the plenum chamber 6 situated beneath the plenum chamber 5, is disposed above the index (not shown) associated with the plenum chamber 5, and is actuated by the solid spindle 19; the other index (not shown) is on the other hand actuated by a hollow shaft (not shown) coaxial with and outside the spindle 19. According to the present invention each plenum chamber 5,6 carries, close to its respective end, a movable contact 20 constituted by a small plate extending outwardly in a direction normal to the axis of the plenum chamber 5, 6 itself. As illustrated in Figure 2, the movable contacts 20 cooperate with cylindrical reference contacts 21 axially slidable within hollow guides 22 which are also substantially cylindrical. These reference contacts 21 have an annularcylindrical relief 23 in an intermediate position, one end of which constitutes a shoulderfor a coil spring 24. This latter rests, atthe opposite end, against an inner annular surface 25 of the guide 22 in such a way as to resist translation of the said reference contact 21 towards the interior of the guide 22 itself.The annular cylindrical relief 23 defines, at the opposite end from thatfacing the spring 24, an axial abutment which, by cooperating with a ring 26 carried atthe inlet of the guide 22, prevents the said reference contact 21 from coming free axiallyfrom the said guide 22. The guides 22, made of conductive material, are externally threaded and screwed into threaded through-holes 27 formed in a conductive element 28, constituted by a small square-section column 29 carrying at its upper end a threaded cylindrical projection 30. The threaded projection 30 engages a hole 31 formed in the support plate 2, and is electrically insulated from it by means of a bush 32 (a cylindrical hollow portion of which is interposed between the said threaded projection 30 and the hole 31), and a washer33, disposed facing the hole 31 from opposite sides in such a way as to coverthe inner surface and periphery thereof. A pair of nuts 34, 35 clamp a first electrical connector 36 to the threaded projection 30 and this to the plate 2. The plate 2, conveniently made of electrically conductive material, isfurtherconnected to a second electrical connector37. In use the threaded spigots 7,8 are connected to two independent pneumatic circuits, for example to the circuits of the braking system acting respectively on the front axle and on the rear axle of the tractor of an industrial vehicle. The mechanisms 9 transmit the displacements of the free ends of the plenum chambers 5, 6 to the associated indices permitting simultaneous reading, in the same instrument, of both pressures. The connectors 36 and 37 are respectively connected to an indicator lamp 38 connected in turn to the positive pole of an electrical battery and to the negative pole of the same battery or conveniently, to elements of the motor vehicle body connected thereto. In the absence of pressure in the pneumatic circuits the plenum chambers (5,6) are undeformed, the movable contacts 20 are pressed againstthe reference contacts 21, which retract into the interior of the guide 22 compressing the spring 24 and closing the electrical circuit. In this condition both plenum chambers are located in the position of the plenum chamber 6 in Figure 2, the lamp 38 is therefore illuminated and thus indicates the condition of insufficient pressure. With an increase in the pressure in one of the pneumatic circuits the associated plenum chamber becomes deformed outwardly and the corresponding movable contact 20 consequently retracts tending to move away from the reference contact 22 facing it. The reference contact 21 is, however, maintained by the spring 24 against the movable contact 20 until the pressure is such thatthe reference contact 21 arrives atthe end of its stroke. The indicator lamp remains illuminated, however, and becomes extinguished only when both the pairs of contacts 20 and 21 are located in this configuration (corresponding in Figure 2 to the position of the plenum chamber 5), that is to say when the pressure level in both pneumatic circuits is such as to guarantee correct actuation of the brakes. The axial position of the guides 22 is adjustable by screwing or unscrewing the guides 22 themselves in the corresponding holes 27; in this way it is possible to adjustthe device to predetermine an appropriate intervention pressure for indication. From a study of the characteristics of the manometerformed according to the present invention the advantages which can be obtained thereby are evident. First of all, the indication of insufficient pressure is indicated through the lamp 38 the illumination of which immediately calls the attention of the driver in the case in which the manometer is installed on a vehicle. The adoption of two plenum chambers which control two indices pivoted about the same axis further allows a single instrumentto be installed ratherthan two as currently takes place, thereby obtaining a reduction both of cost and ofoveral bulk. Finally, it is clearthatthe manometer described above can have modifications and variations introduced thereto without departing from the present invention.

Claims

1. A manometer of the type comprising: at least one curved tubular metal element or plenum chamber, having one end open and fixed and another end closed and free, which can be connected by the said fixed end to an associated pneumatic circuit containing a fluid under pressure and resiliently deform by an amount dependent on the pressure of the said fluid; and mechanism which transform the displacements of the said free end by the effect of the said deformations of the said plenum chamber into rotations of a spindle fixed to an index; characterised by the fact that it includes electrical means operable to indicate a condition of insufficient pressure of the said fluid.

2. A manometer according to Claim 1, characterised by the fact that the said electrical means include a movable contact fixed to the free end of the said plenum chamber and a reference contact.

3. A manometer according to Claim 2, characterised by the fact that the said reference contact is slidably mounted within a guide against the action of resilient means; the said reference contact being able to translate, underthethrust exerted by the said movable contact between afirst contact position corresponding to an undeformed condition of the said plenum chamber, and a limited contact position in which an abutment of the said reference contact meets an abutment stop of the said guide, in the said limit position the said plenum chamber being deformed by the effect of a pressure of pre-determined minimum value.

4. A manometer according to Claim 2 or Claim 3, characterised by the fact that it includes two plenum chambers each of which is provided with corresponding mechanisms actuating the said spindle fixed to the said index and the said movable contacts and reference contacts; the said plenum chambers being disposed in two parallel superimposed planes.

5. A manometer according to Claim 4, characterised by the fact that the said spindles actuating said indices are coaxial, there being a first hollow spindle and a second spindle housed with radial clearance within the said first spindle and free to rotate with respectthereto.

6. A manometer according to Claim 4 or Claim 5, characterised bythefactthatthe said reference contacts are electrically connected to a first connectorwhich can be connected to electrical indicator means.

7. A manometer according to Claim 6, characterised by thefactthat the said electrical indicator means include a lamp.

8. A manometer according to Claim 6 or Claim 7, characterised by the fact thatthe said electrical continuity is formed by the said guides and by a further conductor element connect to the said guides and to the said first connector.

9. A manometer according to Claim 8, characterised bythe factthatthe said guides are substantially cylindrical, externally threaded, and screwed into through-holes in the said further conductor element facing the said movable contacts.

10. A manometer according to any preceding Claim, characterised by the fact that it includes a plate of conductive material supporting and electrically connected to the said plenum chambers and provided with a second connector operable to connect the said plate to electrical supply means.

11. A manometer according to Claim 10, when dependent on Claim 8 or Claim 9, characterised by the fact that the said further conductor element is mounted on the said plate and is electrically insulated with respectthereto.

12. A manometer according to any of Claims from 4to 11, characterised by the fact that the said plenum chambers can be connected to pneumatic braking circuits acting respectively on the front axle and on the rear axle of the tractor of an industrial vehicle.

13. A manometer with insufficient pressure indicator substantially as described and illustrated in the attached drawings.