GB2074253A

GB2074253A - Pressure control apparatus

Info

Publication number: GB2074253A
Application number: GB8109411A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-04-01
Filing date: 1981-03-25
Publication date: 1981-10-28
Also published as: IT8120837A0; FR2479554A1; IT1137321B

Abstract

A pressure control apparatus for controlling a pressure device that tends to overrun after disconnection from its power source has an electric pressure switch combined with a pressure limiting valve, the switch having a pressure member (19) slidable axially in a housing (38) and loaded by the force of a limiter spring (34), that acts on a part of an electric switch (57, 63:72) Figs 16 to 6 (not shown). In order to combine the pressure switch with a pressure limiting valve to relieve excess pressure produced by overrunning, the pressure member (19) is connected on its side remote from the electric switch (57, 63:72) with a valve member (1) of the pressure limiting valve (1, 2) and surrounded by a sleeve member (24) movable in the housing (38), arranged between the pressure member and the housing and on which the limiter spring (34) bears. Between the valve member and the sleeve member a pressure chamber (27a) is provided. The sliding movement of the sleeve member (24) is limited with respect to the valve member (1) by abutments (1, 33; 24, 29 and 70 respectively). <IMAGE>

Description

SPECIFICATION Pressure control apparatus This invention relates to a pressure control apparatus of the kind adapted for connection to control a pressure generating device, such as an electric motor driven pump.

By apparatus of this kind, a control or regulating process can be made dependent on pressure so as, for example, to switch an electric current on or off. The apparatus may be used to monitor the largest and smallest pressures of a hydraulic system. In such apparatus with a sprung switch, altering the tension in the switch spring can alter the pressure at which the switch operates (Werner Dieter, "Oelhydraulikfibel", Krauss-kopf-Verlag, Wiesbaden, 1960, page 187).

By the present invention, a pressure actuated switch can be combined with pressure limiting valve means. Only a single device may be required for performing both functions, the apparatus serving principally to monitor pressure, for example the pressure on the-high pressure side of a pump (e.g. a hydraulic pump) to maintain the same between prescribed limits.

According to the invention, pressure control apparatus is adapted for connection to a press.ure generating device that tends to overrun after disconnection from its power source and combined with pressure limiting valve means that relieve any excess pressure built up by said overrunning.

Said pressure limiting valve means may be operable to connect the said pressure generating device to exhaust and may be so operable at a predetermined pressure just above the pressure at which the apparatus disconnects the pressure generating device from its power source.

The apparatus may comprise pressure controlled electric switch means for controlling said pressure generating device, which may then be a pump, for example a hydaulic pump, driven by an electric motor.

Pressure control apparatus according to the invention may comprise a pressure operated electric switch, having a pressure actuated member slidable axially in a housing against the force of limiter spring and adapted to operate said switch, the pressure actuated member being connected to one member of a pressure relief valve at its end remote from the switch and having a sleeve member also slidable axially in the housing and acted on by the limiter spring, there being a pressure chamber between the said relief valve member and the sleeve, and abutments limiting the relative sliding motion of the said valve member and the sleeve.

The limiter spring may act against a spring load adjustment member axially adjustable in the housing.

The pressure actuated member may be connected to operate the switch by an axially slidable rod that passes through one end of the housing. The axially slidable rod may have a threaded part by which an adjusting knob outside the housing can adjust the spring load adjustment member.

The switch may comprise sprung contact, one of which is moved by the said axially slidable rod.

Alternatively, the switch means may comprise a contactless switch arrangement.

Embodiments of pressure control apparatus according to the invention will now be described with reference to the accompanying drawings, in which: Figures 1 a and 1 b together show a lengthwise section through a first embodiment on the line I-I in Figure 2, Figure 2 is a plan view of the apparatus of Figure 1 with covering parts removed, Figures 3 to 5 are respectively sections on the lines Ill-Ill to IV--IV in Figure 2, Figures 6a and 6b together show a lengthwise section through a second embodiment.

A frustro conical valve member 1 forms with a cooperating member 2, having a valve seat correspondingly conically shaped, a pressure limiting valve. The valve member 1 is, at the smaller end of its conical portion, connected with a valve rod 3, the diameter of which corresponds to the diameter of-the valve seat in member 2, slidably mounted therein. Between the valve member 1 and the valve rod 3 is an annular groove 4 which is connected to an annular duct member 2 to which a lengthwise duct5 is connected which runs in valve member 2 parallel to the axis or inclined to the valve rod 3.

The member 2 is threaded into a housing 6 and packed with a sealing ring 7. It abuts on its side facing away from the valve member 1 against a sealing ring 8 set in the housing base part 6. The housirig base part 6 has an inlet bore 9, connectible to a pump (P) not shown, which is connected with the lengthwise duct 5 by an annular duct arranged between the valve member 2 and the housing 6.

An inlet bore 0 connectible with a reservoir (T), not shown, is connected with a lengthwise duct 11 in the housing 6 arranged parallel to the lengthwise duct 11, which is in connection with the side of the member 2 remote from the annular groove 4.

The housing 6 also has an inlet bore 12, which can be connected with a control device, not shown, or with the pressure side of the pump, not shown. The inlet bore 12 is connected inside the housing 6 with a control duct 1 3 which is arranged coaxial to the valve rod 3 and on the side thereof remote from the valve member 1 and extends through the seal 8.

The valve rod 3 has an extension 14, on its side remote from the valve member 1, which passes through a seal 1 5 which is arranged between annular discs 16 and 1 7. The extension 14, the valve rod 3 and the valve member 1 have a lengthwise through bore 1 8 which extends from the rear side of the extension 14 up to a valve shaft 1 9 which is arranged on the side of the valve member 1 remote from the valve rod 3.

The valve shaft 1 9 is in several parts, having shaft sections 20 to 23. The shaft section 20 is joined directly to the valve member 1 and has the largest diameter. The shaft section 21 is separate from the shaft section 20 and the shaft section 22 from the section 21. The shaft section 23 has a larger diameter than the section 22, but a somewhat smaller diameter than the shaft section 21 . The lengthwise bore 1 8 opens into the shaft section 23.

The valve shaft 1 9 with its shaft sections 20 and 23 is slidable axially in an intermediate sleeve member 24, T-form in lengthwise section. The two opposed end positions are made fluid-tight by seals 25 and 26. Between the seal 25 and the sleeve member 24 are two intervening washers and between the seal 26 and the shaft section 20 of the valve shaft 1 9 is arranged a single washer.

A lengthwise divided, socket-form spacer 27 is inserted on the shaft section 22, which surrounds the opening of the lengthwise bore 1 8 but spaced therefrom, in the region of the shaft section 23.

Into the shaft section 23 of the valve shaft 1 9 is threaded an extension part 28 on its end face remote from the valve member 1. A seal 29a is fastened in between a flange-like part 29 of the part 28 and the valve shaft 19, the diameter of which is greater than the diameter of the shaft section 23 of the valve shaft 19. The part 28 is surrounded by the sleeve member 24 on the end face of which facing away from the valve member 1 is threaded an enlarged end of tube member 30.

The threaded connection is made fluid tight by means of a seal 31. The part 28 reaches into the tube member 30. Between this tube member and the flange-like part 29 of the intermediate part, a switch spring is fastened in.

The end faces facing the seal 25 exert, by means of the pressure built up in the space containing the abutment member 27 a force in the direction to close the valve member 1 and the end face of the valve shaft 19 facing the valve member 1 exerts a force acting in the direction to open the valve member 1. The valve shaft 1 9 forms among other things a pressure member which, by virtue of the pressures on it, exerts a force in the direction to close the valve member 1.

The sleeve member 24 has a flange 33 on its side facing the valve member 1 , which serves to abut the limiter spring 34, which abuts on the side facing away from it a piston-forming member 35.

In an annular groove on the outside of the member 35, a seal 36 is inserted. The member 35 is traversed by the tubular part 30, having an enlarged end in the region of the sleeve member 24. Where the part 30 passes through the member 35 is made fluid tight by an annular seal 37 inserted in the member 35.

The sleeve member 24 and the member 35 are contained in a cylindrical housing part 38 which is rigidly connected with the housing base part 6. On the side remote from the part 6, a hoilow adjusting screw 39 is screwed into the housing part 38 which abuts against the member 35 through the intermediary of two spacing washers 40,41 of different diameters. The position of the member 35 is determined by the position of the adjusting screw 39 in the housing part 38.

A switch housing 42, connected to the housing part 38 by screws 43, is closed on its side remote from the housing piece 38 by an annular cover 44, through which passes an adjusting shaft 45 on which, outside the switch housing 42, an adjusting knob 46 is fastened. The adjusting shaft 45 terminates, in the region-of the housing part 38, in a cylindrical part 47 which surrounds the near end of the adjusting screw 39. The cylindrical part 47 has a lengthwise slot 48 into which extends radially a connector 50, having a roller 49, which is fixed in the adjusting screw 39. The cylindrical part 47 is guided, in a guide ring 51 carried in the switch housing 42 by its end remote from the adjusting knob 46, the ring 51 being arranged on the end face of the annular part 47 and abutting the annular abutment 52 carried by the housing piece 38.

Inside the tubular part 30 extends a switch rod 53 which is threaded into the part 28. The rod 53 supports, by means of a ball bearing 54, an intermediate member 55 in the cylindrically formed part 47 of the adjusting shaft 45, on which a contact carrier 56 abuts, on which a plastic discshaped contact-carrying body 57 is fastened by screws.

Between the intermediate member 55 and the end of the tubular part 30 that projects into the cylindrical part 47 of the adjusting rod 45 is arranged in an intermediate member 55a on which a second contact carrier 58 abuts. The flange of this contact carrier is, on opposite sides of each square cross-sectioned foot of a carrying cylinder 61 traversed with freedom to slide and which the contact body 56 aios passes through with freedom to slide. In the carrying cylinder 61, a two-part insulating plastic bush 60 is inserted.

The bushes 60 and 61 are connected together by a screw 59. On the flange of the insulating bush 60 a contact ring 63 is pressed, by means of a spring 62, which, in the position shown, lies on the contact body 57, whereby the circuit is closed and the pump is turned on (Figure 3). The heads of the securing screws 59 are lined up with bores in the cover 44 which are closed off by flush screws.

The insulating sleeve 60 has a radially outwardly extending supporting part for the contact ring 63.

This supporting part is not operative in the shown position, only when the contact carrier 58 is lifted with regard to the contact carrier 56 and brought nearer thereto.

Between the flange-like part of the contact carrier 56 on the one side, and each of the two nuts 65 on the other side, is a spring 66 (Figure 4).

The nut 65 is threaded on to a bolt 65a which goes through the contact carriers 56 and 58 with play and with the end remote from the nut 65 screwed into the switch housing 42. On the other end of the screw bolt 65a is threaded a retaining nut with its flange sunk into the cover 44 to secure the same.

Into the switch housing 42, as seen in Figure 5, are threaded two securing bolts 67 axially parallel to the switch rod 45 and lying-on opposite sides, which are each surrounded by a spring 68. The spring presses, at one end, on the head of the securing belt 67 and, at its other end, on the contact carrier 58. The securing bolts 67 pass through with play, the contact carrier 58, but do not extend to the contact carrier 56.

The switch spring 32 can be dispensed with.

The washer 41 is composed of plastic and forms an axial bearing for the washer 40.

The whole arrangement of the switch apparatus is so designed that with the pressure limiting valve closed and no pressure in the space 27a containing the spacer 27, the contacts of the contact rings 63 and 57 lie against each other and the switch is closed, so that a drive motor (not shown) of a pump (not shown) is connected to a current supply, but that at a predetermined pressure in the circuit at which the intermediate member 24 has been moved back a predetermined amount in regard to the valve member 1 , this switch opens, so that the drive motor of the pump is cut off from the current supply.

The pressure in the control duct 13 acts in the space 27a containing the spacer 27 through the lengthwise bore 1 8. It acts in the sense of closing the valve member 1 and exerts a force on the sleeve member 24 tending to move it in the direction of the adjusting knob 46. At a certain pressure, the contact carrier 58 will lift and open one catact of the pressure switch. The drive motor of the pump is still running. If on further lifting of the contact carrier 58 the other contact of the pressure switch is also opened, the drive motor of the pump is cut off from its current supply.

Because of the overrunning of the drive motor and the pump as a result of the inertia of the rotating masses the pressure will increase in the.

hydraulic system. Shortly after opening the two switches, the intermediate member 24 is adjacent the flange-like part 29 and the valve member 1 is lifted from its seat on the member 2, so that the pressure limiting valve 1,2 is open. The whole arrangement is by virtue of this so designed that the pressure at which the drive motor of the pump is cut off from its current supply is only a little less than the pressure at which the pressure limiting valve 1,2, opens.

It, when the drive motor of the pump is stopped the pressure falls in the hydraulic circuit, the pressure limiting valve 1,2 closes and the sleeve member 24 moves in the direction of the valve member 1. First one and then the other contact of the pressure switch closes. On closure of the second contact, the drive motor of the pump is connected with its current supply. The pump runs and the pressure in the hydraulic circuit is built up again. The just described process is then repeated.

In this manner it is possible to maintain a predetermined pressure in the hydraulic circuit within narrow limits. A special pressure monitor to control pressure in the hydraulic circuit can be dispensed with.

The pressure required to open the pressure limiting valve is equally as large as the operating pressure in the hydraulic system. As long as the pressure limiting valve 1,2 is closed, the switch maintains the operating pressures with a predetermined range. The predeterminable range of the operating pressures can be adjusted by means of the screw 59, by which when the switch is open the spacing between the contact plate 57 and the switch ring 63 can be altered.

By turning the adjusting wheel 46 the pretension of the spring 34 is altered and thereby the pressure at which the drive motor of the pump is switched off and the pressure at which the pressure limiting valve 1,2 opens' are simultaneously altered. The switching pattern of the pressure switch, that is to say the adjusted pressure range, is independent of the opening pressure of the pressure limiting valve 1, 2.

Depending on the opposed pressure faces in the space 27a and/or depending on the characteristic of the limiting spring 34 and/or the arrangement and selection of the switch spring 32, different switching characteristics can be achieved.

The second embodiment according to Figure 6a and 6b has substantia! parts of the first embodiment, which are indicated with the same reference numbers. The second embodiment has two lengthwise ducts 5 running inclined to the valve rod 3. The vaLve shaft 19 also has shaft parts 20, 21 and 23. The shaft part 21 is separate from the shaft part 20; The shaft-part 23 has a somewhat smaller diameter than th.e shaft part 21. No part corresponating ito the spacer 2.7 of the first embodiment is proy'rdeci:hokvever. Instead of the seal 29a, a abutnient r 7.t() is provided, the diameter of which is grn-ater-'th'an':the diameter of the shaft part 23 of the valve shaft 19.Into the sleeve member 24 is threaded one end of a tubular part 30 of a switch rod 53a, on the end face remote from the valve member 1. Between the base of the tubular part 30 and the flange-like part 29 of the part 28 is a spring 32.

The end faces facing the seal 25 exert a force, as a result of the pressure built up in the space 27a, in the direction to close the valve member 1 and the end faces facing the valve member 1 exert force in the direction to open the valve member 1.

The valve shaft 1 forms also among other things a pressure member, which by virtue of the pressure acting on it exerts a force in the direction to close the valve member 1.

The member 35 is traversed by the switch rod 53a at its end having the tubular part 30. The hollow adjusting screw 39 is supported on the member 35 with the interposition of a ball bearing 40a and the washer 41.

The housing part 38 is, on the side remote from the base 6 of the housing, covered by an annular closure 44 which the adjusting shaft 45 passes through, an ajusting part 46a being located on the outside of the housing part 38. The cylindrical part 47 is guided on its end remote from the adjusting part 46a in the housing part 38. The switch rod 53a supports the peg-form intermediate member 55a which is in the cup-shaped part 47 of the adjusting shaft 45, the switch body 56a being supported on the member 55a and being carried in a bearing 71 on the adjusting shaft 45. Between the switch body 46a and the closure 44 is a spring 66. The switch body 46a cooperates with a switch 72 arranged radially on the housing part 38 and radially adjustable relative to the housing part 38, and which is contactless switch.

The whole arrangement of the switch apparatus is so designed that with the pressure limiting va'lve closed and pressure off the space 27a, the switch 72 is closed, so that a drive motor (not shown) of a pump (not shown) is connected with a current supply, but that at a certain predeterminable pressure in the control circuit, at which the intermediate member 24 has been moved back a predetermined distance with respect to the valve member 1 , the switch 72 opens, so that the drive motor of the pump is cut off from the current supply.

As previously explained, the hydraulic parts of the first and second embodiments correspond.

Only in the construction of the switch are there to be found more substantial differences.

Also in the second embodiment the pressure in the control duct 13 acts through the lengthwise bore 18 in the space 27a in the sense to close the valve member 1 and exerts a force on the sleeve member 24 in the direction tending to displace the adjusting part 46a. At a certain pressure the switch 72 will open and the drive motor of the pump will be disconnected from the current supply. Shortly after opening the switch, the sleeve member 24 hits the abutment ring 70 and the valve member 1 will be lifted from its seat on the counter member 2, so that the pressure limiting valve 1, 2 opens. The pressure at which the drive motor of the pump is disconnected from the current supply is only a little less than the opening pressure of the pressure limiting valve 1, 2. When the pressure falls in the hydraulic circuit the pressure limiting valve 1,2 closes and the intermediate member 24 moves in the direction of the valve member 1. On closing the switch 72 the drive motor of the pump is again connected to the current supply.

As long as the pressure limiting valve 1, 2 is closed, the switch 72 holds the operating pressure within a certain range independent of its adjustment position. By turning the adjusting part 46a the pre-loading of the spring 34 is altered and thereby the pressure at which the drive motor of the pump switches off, and the pressure at which the pressure limiting valve 1,2 opens is likewise altered.

Claims

1. Pressure control apparatus adapted for connection to control a pressure generating device that tends to overrun after disconnection from its power source, combined with pressure limiting valve means that relieve any excess pressure built up by said overrunning.

2. Apparatus according to claim 1, said pressure limiting valve means being operable to connect the pressure generating device to exhaust.

3. Apparatus according to claim 1 or claim 2, said pressure limiting valve means being operable to relieve excess pressure at a predetermined pressure just above the pressure at which the apparatus disconnects the pressure generating device from its power source.

4. Apparatus according to any one of claims 1 to 3 comprising pressure controlled electric switch means for controlling said pressure generating device.

5. Apparatus according to any one of claims 1 to 4, said pressure generating means comprising a pump.

6.Pressure control apparatus comprising a pressure operating electric switch, having a pressure actuated member slidable axially in a housing against the force of a limiter spring and adapted to operate said switch, the pressure actuated member being connected to one member of a pressure relief valve at its end remote from the switch and having a sleeve member also slidable axially in the housing and acted on by the limiter spring, there being a pressure chamber between the said relief valve member and the sleeve, and abutments limiting the relative sliding motion of the said valve member and the sleeve.

7. Apparatus according to claim 6, in which the limiter spring acts against a spring load adjustment member axially adjustable in the housing.

8. Apparatus according to claim 6 or claim 7, in which the pressure actuated member is connected to operate the switch by an axially slidable rod that passes through one end of the housing.

9. Apparatus according to claim 7 or claim 8 in which the axially slidable rod has a threaded part by which an adjusting wheel outside the housing can adjust the spring load adjustment member.

10. Apparatus according to claim 9, in which the switch comprises sprung contacts one of which is moved by the said axially slidable rod.

11. Apparatus according to any one of claims 6 to 10 in which the switch means comprise a contactless switch arrangement.