GB2044895A

GB2044895A - Adjustable control

Info

Publication number: GB2044895A
Application number: GB7909316A
Authority: GB
Original assignee: METERING PUMPS Ltd
Current assignee: METERING PUMPS Ltd
Priority date: 1979-03-16
Filing date: 1979-03-16
Publication date: 1980-10-22
Also published as: GB2044895B

Abstract

A control knob (20) of a stroke adjustor mechanism (2) of a reciprocating pump drive mechanism (1) is axially movable between a first position in which gearing (24) on the control knob is fixedly engaged with gearing formed on the stroke adjustor housing (23), and a second position in which the gearing (24) is disengaged to allow rotation of the control knob for rotating an actuating screw (17) carrying a stop (15) for defining the limit of the return stroke of the pump drive member (3). <IMAGE>

Description

SPECIFICATION Adjustable control The present invention relates to an adjustable control and in particular to an adjustable control having a mechanism for a control knob which can have its rotational portion locked when a particular setting has been selected.

It is known to provide a control knob which is able to be held against rotation. For example, our British Patent Specification No.

1,176,933 discloses a stroke adjustor mechanism for a reciprocating pump where the control knob for the reciprocating pump has a spur gear which also connects the control knob to a stroke indicator and/or to a stroke controlling mechanism, and a spring plunger is provided for engaging between two adjacent teeth of the spur gear for locking the stroke adjustor control knob against rotation once a particular setting has been achieved.

This locking action requires a strong spring on the plunger if there is to be no likelihood of the locking effect being destroyed by the vibration which a reciprocating pump drive generates, and it is also necessary to seal the plunger against either escape of lubricant or contamination by ingress of foreign bodies into the interior of the stroke adjustor housing.

The present invention aims to provide a control mechanism in which a more robust locking system is provided and which does away with the spring loaded plunger.

In accordance with the present invention we provide an adjustable control comprising control knob, a housing in relation to which said control knob is rotatable, and gearing carried by said housing and said control knob for selective engagement and disengagement whereby upon engagement of the gearing the gearing carried by the housing is stationary and prevents rotation of the control knob.

The gearing mounted on the housing may, for example, comprise a ring gear of the same pitch circle as a spur gear constituting the said gearing on the control knob and may advantageously be engageable with the spur gear by axial movement of the control knob; alternatively the said gearing mounted on the housing may comprise a rack which is engageable with a spur gear constituting the gearing on the control knob, for example by axial movement of the control knob.

In order that the present invention may more readily be understood the following description is given, merely by way of example, reference being made to the accompanying drawings in which: Figure 1 is a side elevational view, partly in section, of a drive mechanism for a reciprocating pump and showing the adjustable control in accordance with the present invention; and Figure 2 is a horizontal section through the stroke adjustment mechanism of Fig. 1, taken on the line Il-Il of Fig. 1.

In Fig. 1, there can be seen the drive mechanism 1 for a reciprocating type pump head (not shown) and this drive mechanism 1 has at its left-hand end a stroke mechanism generally referenced 2.

The operating principle of the stroke adjustment mechanism for the drive unit 1 is that an adjustable stop shortens the return yoke 3 as it is moved leftwardly under the influence of a helical compression spring 4.. At its righthand end, the yoke 3 has a pump head drive shaft 5 sliding in a bush 6 and provided with a counter bore 7, threaded at 8, to engage the piston rod, or other drive member, of the pumping head (not shown). Likewise, at its left-hand end the yoke 3 has a guide rod 9 which slides in a bush 10 as the yoke is reciprocated, rightwardly under the influence of the outer race 11 of a ball-bearing assembly 1 2 carried by an eccentric 1 3 on the drive shaft 14, and leftwardly by the spring return action.

A relatively stiff, but nevertheless to some extent resilient, buffer stop 1 5 in the stroke adjustment mechanism 2 provides a stop against which the left-hand end of the guide rod 9 of the yoke abuts to define the limit of the return stroke. Once the guide rod 9 is in contact with the buffer stop 1 5 the yoke remains stationary until the drive shaft 1 4 has rotated far enough to bring the outer race 'i 1 of the eccentric ball bearing assembly 1 2 once again into contact with the yoke 3 to drive it rightwardly for a pump discharge stroke starting with retraction of the guide rod 9 off the buffer stop 1 5. It is the position of the buffer stop 1 5 which is adjustable rightwardly and leftwardly which serves to vary the pump stroke.

The buffer stop 1 5 is secured, by means of a stud 16, to an actuating screw 1 7 whose head is splined at 1 8 to cooperate with internal splines 1 9 formed on a control knob 20.

The shank of the screw 1 7 threadedly engages at 21 with a sleeve 22 which is nonrotatably fixed, and held against axial motion, in the pump drive unit body.

From the above, it will be understood that rotation of the control knob 20 effects rotation of the splined head of the actuating screw 1 7 and this in turn, by virtue of the cooperating threads 21 between the shank of the actuating screw 1 7 and the fixed sleeve 22, effects rightward and leftward movement of the actuating screw 1 7 together with the buffer stop 1 5 carried thereby. Hence rotating the control knob 20 in one direction will shorten the punp stroke and rotation in the opposite direction will lengthen the pump stroke.

It is desired that the control knob 20 should hold any given position, once selected, despite the effect of vibrations from the drive action of the pump head, from the eccentric 13, from the various orbiting masses carried thereby, as well as from the reciprocation of the yoke 3. This holding is achieved by mounting the control knob 20 axially slidably within a housing 23 and on the outside of the sleeve 22, the engagement between the control knob 20 and the housing 23 being effected by way of cooperating external gear teeth 24 on the control knob and an internal or ring gear formation, in the housing.

Thus, when the control knob 20 is in the Fig. 1 position, the cooperation of the gear teeth 24 of the control knob 20 with the ring gear formation on the housing 23 holds the control knob against rotation. On the other hand, when the control knob 20 is pressed inwardly, i.e. moved rightwardly, to disengage the gear teeth 24 from the ring gear formation in the housing 23 the control knob is released for rotation which will in turn entrain the actuating screw 1 7 for rotation and move the resilient buffer stop 1 5 along the axis of the guide rod 9 of yoke 3.

In order to avoid ingress of dirt into the interior of the housing 23 during this sliding movement, an O-ring seal 25 is captive in the opening at the left hand end of the housing 23 and allows the control knob 20 to be both rotated and axially moved relative to the housing 23 without loss of sealing action.

The control knob 20 includes projecting resilient claws 26 having tips 27 which are engageable in either of two V-section grooves 28 formed on the exterior of the sleeve 22.

These define "check stops" at the two extreme positions during movement of the control knob between its locked position illustrated in Fig. 1 and the "free" position rightwardly spaced from the Fig. 1 position.

During axial sliding movement of the control knob 20 relative to the housing 23, splines 29 of the control knob remain in engagement with a gear 30 of a three digit revolution counter 31 which thus displays an indication of the pump stroke. In practice, the diameter of the control knob 20 at the splines 29 is related to the size of the gear 30 such that the full range of stroke adjustment can be represented as 100% of movement indicated by the revolution counter and hence the revolution counter will at any time indicate the percentage of full stroke to the first place of decimals.

The top plan view of Fig. 2 shows the same mechanism, and illustrates a window 32 in which the stroke reading can be seen from outside.

In the embodiment of control knob illustrated in Figs. 1 and 2, the "locked" position of the knob is held by engagement of an external gear on the control knob with an internal gear on the housing. It will of course be appreciated that the scope of the present invention embraces the possibility of the control knob having an internal gear and the housing having an external gear, if this should for any reason prove desirable.

Furthermore, it is not essential that the fixed gearing be in the form of an internal gear to cooperate with gear teeth on the control knob. It is alternatively possible for the fixed gearing to comprise either a pinion or a rack which can be selectively engaged with gearing on the control knob but will, once engaged, be stationary with respect to the housing. Thus it is not essential that the engagement and disengagement of the fixed gearing and the gearing on the control knob be achieved by reciprocation of the control knob; it is for example possible for the gearing mounted on the housing to be movable from a disengaged position to an engaged, and fixed position. For example, where a rack is used as the gearing on the housing the rack may be pivotable onto the control knob gear and thus be self-wedged to resist any rotation of the control knob.

Straight toothed gearing is preferred where axial shifting of the control knob is used to effect engagement and disengagement of tne gearing because this will hold the control knob 20 against rotation during sliding.

Although, in the present application, the stroke adjustor control knob 20 is directly splined at 1 8 to the head of the actuating screw 1 7 of the stroke adjustor, it would alternatively be possible for the control knob to be provided with a spur gear which meshes with spur gearing to the stroke adjustor actuating member where, for example, some stepdown or step-up ratio between the control knob and the actuating shaft may be required.

In those circumstances, it is envisaged that the spur gear on the control knob will be in constant mesh with the spur gearing to the actuating member during axial movement of the control knob between its "locked" and "free" positions.

Claims

1. An adjustable control comprising control knob, a housing in relation to which said control knob is rotatable, and gearing carried by said housing and said control knob for selective engagement and disengagement whereby upon engagement of the gearing the gearing carried by the housing is stationary and prevents rotation of the control knob.

2. A control according to claim 1, wherein said control knob is axially movable and engagement and disengagement of said gearing on the control knob and on the housing is achieved by way of the axial movement of the control knob.

3. A control according to claim 2, and including detent means for holding said control knob in either one of two extreme positions of its axial movement.

4. A control knob according to claim 2 or 3, wherein said control knob is internally splined and engages external splines on an actuating shaft.

5. A control according to claim 4, wherein said actuating shaft is externally threaded and cooperates with a threaded sleeve for axial movement of said actuating shaft in response to rotation of said control knob.

6. A control according to any one of the preceding claims, wherein said gearing on the control knob is external gearing and said gearing on the housing is in direct engagement with said gearing on the control knob.

7. A control according to claim 6, wherein said gearing on the housing is a rack engageable with the said external gearing on the control knob.

8. A control according to claim 7 when claim 6 is appendant to any one of claims 2 to 5, wherein said rack is movable from a disengaged position to an engaged position in which engaged position the rack is held and locks the control knob against rotation.

9. A control according to claim 6, wherein said gearing on the housing is internal gearing formed on the housing.

10. A control according to any one of the preceding claims, and including external splines on said control knob for engagement with a rotation counter.

11. A stroke adjustor for a reciprocating drive mechanism, and incorporating a control knob according to claim 5, wherein said actuating shaft carries a stop for defining the limit of spring-biased return movement of a drive member which is driven in a forward direction by means of an eccentric mechanism.

1 2. A control substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

1 3. A drive mechanism for a reciprocating pump head, such drive mechanism being substantially as hereinbefore described with reference to, and as illustrated in, the accompanyzz ing dr3lwings.

CLAIMS (1 Jan 1980)

1. An adjustable control comprising a rotatable actuating shaft, a control knob axially movable with respect to and splined on said actuating shaft, a housing in relation to which said control knob is rotatable and axially movable, a rotation counter connected to said control knob; wand gearing carried by said housing and said control knob for selective engagement and disengagement upon axial movement of said control knob, the gearing carried by the housing being stationary, whereby upon engagement of the gearing rotation of the control knob is prevented.