GB2354053A - Spring retention - Google Patents

Abstract

A spring retention arrangement (11) comprises first and second spring abutment members (26, 34) and a spring (25) engaged between the first and second spring abutment members (26, 34). The first and second spring abutment members (26, 34) are provided with integral features (27, 36) arranged to cooperate with one another to limit relative axial movement between the first and second spring abutment members (26, 34). Alternatively, the spring retention arrangement (11) may comprise a spring abutment member arranged to be mounted upon a housing, such as a housing forming part of a unit pump/injector (10) or a unit pump, the spring abutment member being provided with resilient features permitting mounting of the spring abutment member upon the housing in a snap-fit manner.

Description

2354053 SPRING RETENTION This invention relates to a spring retention

arrangement particularly suitable for use with a fuel pump, for example the pump of a unit pump/injector.

It is increasingly common to use automated "pick and place" devices in assembly lines. Where such a device is used in the assembly process for an engine of the type which uses unit pump/injectors, then it is important to ensure that all of the components of the pump/injector are retained in position whilst the pump/injector is being positioned and subsequently secured in position. It is further convenient for the plunger return spring to be used by the pick and place device to hold the unit pump/injector, thus the spring must be rigidly secured to the unit pump/injector. It is an object of the invention to provide a spring retention arrangement in which all of the components of the arrangement are retained and which permits secure mounting of the spring to a unit pump/injector.

According to the present invention there is provided a spring retention arrangement comprising first and second spring abutment members, and a spring engaged between the spring abutment members, wherein the first and second spring abutment members are provided with integral features arranged to cooperate with one another to limit relative axial movement between the spring abutment members.

The features conveniently comprise inwardly projecting regions provided on one of the abutment members and outwardly projecting regions provided on the other of the abutment members. The inwardly projecting regions 2 conveniently define therebetween recesses through which the outwardly projecting regions can pass on assembly.

Means may further be provided to limit relative angular movement between the spring abutment members.

The means conveniently comprise inwardly projecting tabs provided on the said one of the abutment members arranged to cooperate with the outwardly projecting regions of the other abutment member.

The invention also relates to a method of assembling such an arrangement comprising the steps of locating the spring on the first spring abutment member locating the second spring abutment member on the spring, compressing the spring, moving the features of the second abutment member past those of the first abutment member, moving the second abutment member angularly relative to the first abutment member and allowing the spring force to urge the features to cooperate with one another.

According to another aspect of the invention there is provided a spring retention arrangement comprising a spring abutment member arranged to be mounted upon a housing, the spring abutment member being provided with resilient features permitting mounting of the spring abutment member upon the housing in a snap-fit manner.

The housing conveniently forms part of a unit pump/injector or unit pump.

3 The spring retention arrangement conveniently further comprises means for securing a moveable part of the pump to the housing, the moveable part comprising, for example, a pumping plunger.

The two aspects of the invention may be used in combination with one another.

It will be appreciated that such an arrangement is advantageous in that it permits secure mounting of the spring to a pump with the result that the pump can be manipulated using the spring, the various parts of the spring retention arrangement and moveable part(s) of the pump all being securely retained upon the pump housing.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a sectional view of a unit pump/injector provided with a spring retention arrangement in accordance with an embodiment of the invention; Figure 2 is a side view of one of the spring abutment members of the spring retention arrangement shown in Figure 1; Figures 3 and 4 are sectional views along the lines X-X and Y-Y of Figure 2, respectively; Figure 5 is a plan view of the abutment member of Figure 2; 4 Figure 6 is a side view of the other abutment member of the arrangement shown in Figure 1; Figure 7 is a sectional view along the line Z-Z of Figure 6; Figure 8 is an enlargement of part of Figure 7; and Figure 9 is a view of the abutment member of Figure 6 from beneath.

Figure 1 illustrates a unit pump injector 10 with which a spring retention arrangement 11 in accordance with an embodiment of the invention is used. Although the description herein is of the use of the spring retention arrangement with a unit pump injector, it will be appreciated that the spring retention arrangement is suitable for use in other applications and with other types of fuel pump, for example unit pumps which are spaced physically from associated fuel injectors, the outlets of the pumps being connected to respective fuel injectors using suitable high pressure fuel pipes. It will further be appreciated that the spring retention arrangement is suitable for use with other types of unit pump/injector than the particular type described herein. For example, although the description herein is of a unit pump/injector in which the timing of commencement of fuel injection is determined by the timing of pressurization of fuel, the invention is also suitable for use with unit pump injectors of the type in which the timing of commencement of injection can be controlled independently of the injection pressure.

The unit pump/injector illustrated in the accompanying drawings Comprises a nozzle body 12 having a blind bore formed therein within which a needle 13 is slidable. The needle 13 is engageable with a seating to control the flow of fuel from a delivery chamber 14 past the seating to one or more outlet openings located downstream of the seating. The needle 13 is biased by a spring 15 towards its seating. The needle 13 is provided with angled thrust surfaces 16 exposed to the fuel pressure within the delivery chamber 14 and orientated such that when the delivery chamber 14 is charged with fuel to a high pressure, a force is applied to the needle 13 urging the needle against the action of the spring 15 away from its seating to permit fuel delivery through the outlet openings.

The delivery chamber 14 communicates through a supply passage 17 with a pump chamber 18 defined within a pump housing 19. The pump housing 19 is provided with a through bore 20 within which a pumping plunger 21 is reciprocable. The pumping chamber 18 is defined, in part, by the bore 20 and lower end surface of the plunger 21.

The pumping chamber 18 further communicates through a passage 22 with a port of an electromagnetically actuable spill valve arrangement 23. The spill valve arrangement 23 controls communication between the passage 22 and a fuel inlet port 24 which is connected, in use, to a suitable low pressure fuel reservoir.

The pumping plunger 21 is arranged such that, in use, it is driven in an inward direction through a cam and tappet arrangement (not shown) and is subsequently withdrawn from the bore 20 to increase the volume of the pumping chamber 18 under the action of a return spring 25 forming part of the spring retention arrangement 11. The return spring 25 sits upon a first spring abutment member 26 which includes, at its lowermost end, an 6 outwardly extending flange 27 including an upper surface forming a spring abutment surface with which the spring 25 engages. The flange 27 sits upon part of the pump housing 19. The first spring abutment member 26 is illustrated most clearly in Figures 2 to 5 and includes a region 28 of substantially tubular form which extends upwardly from the inner periphery of the flange 27. The upper end of the tubular region 28 is connected to an inwardly extending flange 29 which is of generally annular form and which is provided, as illustrated in Figure 5, with a pair of diametrically spaced recesses 29a.

The tubular region 28 is provided, adjacent the outwardly extending flange 27, with a pair of inverted U-shaped slots 30 which define tabs 3 1. As shown most clearly in Figure 3, the tabs 31 are bent in an inward direction. The tubular region 28 is further provided, adjacent the inwardly extending flange 29, with four generally C-shaped slots 32 which define tabs 33. As illustrated in most clearly in Figure 4, each of the tabs 33 is bent in an inward direction.

As illustrated in Figure 1, the end of the return spring 25 remote from the first spring abutment member 26 engages a second spring abutment member 34 which is illustrated in more detail in Figures 6 to 9. The spring abutment member 34 comprises a tubular sleeve 35, the upper end of which is provided with a radially outwardly extending flange 36, the lower surface of which engages the return spring 25. The lower end of the tubular sleeve 34 is provided with a pair of radially outwardly extending projections 37 which are diametrically opposed. As illustrated in Figure 9, the outer edges of the projections 37 are spaced apart from one another by a distance a which is greater than the diameter of the inner periphery of the flange 29 and greater 7 than the distance b marked on Figure 4 which represents the spacing between opposite ones of the tabs 33.

Figure I illustrates the spring retention arrangement in an assembled condition. In order to assemble the spring retention arrangement prior to mounting the arrangement upon the remainder of the pump, the spring 25 is located upon the flange 27 of the first spring abutment member 26. The second spring abutment member 34 is then positioned upon the spring 25 with the projections 37 aligned with the recesses 29a of the inwardly extending flange 29 of the first spring abutment member 26. The spring is compressed to bring the projections 37 through the recesses 29a of the flange 29, and the second spring abutment member 34 is then rotated relative to the first spring abutment member 26 through 90". The rotation of the second spring abutment member 34 results in the projections 37 riding over opposite ones of the tabs 33, deflecting the tabs 33 in an outward direction, continued rotation of the second spring abutment member 34 resulting in the projections 37 moving out of engagement with the tabs 33 whereon the tabs 33 return to the position illustrated in Figure 4. Once this position has been reached, it will be appreciated that relative angular movement between the first and second spring abutment members 26, 34 is restricted by engagement between the projections 37 and the ends of the tabs 33. The first and second spring abutment members 26, 34 are then allowed to separate under the action of the spring 25. The spring 25 moves the first and second spring abutment members 26, 34 to a position in which the projections 37 engage the underside of the flange 29, in this position the spring 25 being slightly compressed. It will be appreciated that in this condition, separation of the first and second spring abutment members 26, 34 and the spring 25 is not permitted.

8 After assembly of the spring retention arrangement, the spring retention arrangement is secured to the pump body 19 by inserting the first spring abutment member 26 over a projection 19a of the pump body 19. The projection 19a is a close fit within the tubular sleeve 28, the movement of the spring abutment member 26 over the part 19-a causing the tabs 31 to deflect outwardly. As illustrated in Figure 1, the pump housing 19 is provided with a pair of recesses or an annular groove or recess into which the tabs 31 move when the first spring abutment member 26 reaches the position illustrated in Figure 1, to secure the spring retention arrangement to the pump housing in a snap fit manner. The engagement between the tabs 31 and a shoulder 19b deftned by the recess formed in the part 19a secures the spring retention arrangement to the pump body 19 and thus permits manipulation of the pump using the spring 25.

After securing the spring retention arrangement to the pump housing 19, the plunger 21 is inserted into the bore 20 and moved to a position in which an enlarged head 21a of the plunger 21 engages a step 35a formed in the wall of the tubular part 35. A load transmitting load member 38 is introduced into the tubular part 35 and is retained in position using an O-ring or circlip 40 which is located within an annular groove 40a formed adjacent the upper part of the second spring abutment member 34. The provision of the O-ring or circlip 40 prevents or reduces the risk of the plunger 21 and load transmitting member 39 becoming separated from the remainder of the unit pump/injector 10 during manipulation. It will be appreciated, therefore, that the pump/injector 10 is suitable for use in an automated assembly line.

Claims (10)

1. A spring retention arrangement comprising first and second spring abutment members, and a spring engaged between the first and second spring abutment members, wherein the first and second spring abutment members are provided with integral features arranged to cooperate with one another to limit relative axial movement between the first and second spring abutment members.

2. The spring retention arrangement as claimed in Claim 1, wherein the features comprise inwardly projecting regions provided on one of the abutment members and outwardly projecting regions provided on the other of the abutment members.

3. The spring retention arrangement as claimed in Claim 2, wherein the inwardly projecting regions define therebetween recesses through which the outwardly projecting regions can pass upon assembly of the arrangement.

4. The spring retention arrangement as claimed in any of Claims 1 to 3, further comprising means for limiting relative angular movement between the first and second spring abutment members.

5. The spring retention arrangement as claimed in Claim 4, wherein the means for limiting relative angular movement between the first and second spring abutment members comprise inwardly projecting tabs provided on the said one of the abutment members which is arranged to cooperate with the outwardly projecting regions of the other abutment member.

6. A method of assembling the spring retention arrangement as claimed in any of Claims 1 to 5, comprising the steps of; locating the spring on the first spring abutment member, locating the second spring abutment member on the spring, compressing the spring, moving the features of the second abutment member past those of the first abutment member, moving the second abutment member angularly relative to the first abutment member, and allowing the spring force to urge the features to cooperate with one another.

7. A spring retention arrangement comprising a spring abutment member arranged to be mounted upon a housing, the spring abutment member bei provided with resilient features permitting mounting of the spring abutment member upon the housing in a snap-fit manner.

8. The spring retention arrangement as claimed in Claim 7, wherein the housing forms part of a unit pump/injector or a unit pump.

9. The spring retention arrangement as claimed in Claim 7 or Claim 8, further comprising means for securing a moveable part of the pump to the housing.

11

10. The spring retention arrangement as claimed in Claim 9, wherein the moveable part of the pump comprises a pumping plunger.