US3766340A

US3766340A - Electrical contact breaker apparatus for spark ignition internal combustion engines

Info

Publication number: US3766340A
Application number: US00261713A
Authority: US
Inventors: B Richards
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-06-16
Filing date: 1972-06-12
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16
Also published as: GB1395492A

Abstract

The invention is concerned with Electrical contact breaker apparatus for spark ignition internal combustion engines, the apparatus including a set of electrical contact points and a follower member for contacting a cam rotatably mounted in an electrical distributor for opening and closing said contact points, the electrical contact points and the follower being incorporated in a replaceable cartridge adapted for slide mounting in the distributor.

Description

United States Patent 1 91 Richards ELECTRICAL CONTACT BREAKER APPARATUS FOR SPARK IGNITION INTERNAL COMBUSTION ENGINES [76] Inventor: Brian Richards, 38 Towngate,

Newsome, Huddersfield, Yorkshire, England [22] Filed: June 12, 1972 [21] Appl. No.: 261,713

[30] Foreign Application Priority Data June 16, 1971 615111111155 Nov. 27, 1971 Great Britain 52] US. c1..;..;;I...;."20'6/30' A, 560/19 A, 206/31 A 51 Int. Cl. H0111 19/62, 110111 9/08 [58] Field of Search zoo/'19 R, 19 A, 30 A,

200/30 AA, 31 R, 31 A [56] References Cited UNITED STATES PATENTS 3,339,049 8/1967 Gover 200/19 A X 1 Oct. 16, 1973 3,055,992 9/1962 Sargis 200/30 A 3,629,527 12/1971 Fry 200/19 A 3,581,025 5/1971 Yeo 200/19 A Primary Examiner-J. R. Scott Attorney-Norris & Bateman [5 7] ABSTRACT The invention is concerned with Electrical contact breaker apparatus for spark ignition internal combustion engines, the apparatus including a set of electrical contact points and a follower member for contacting a cam rotatably mounted in an electrical distributor for opening and closing said contact points, the electrical contact points and the follower being incorporated in a replaceable cartridge adapted for slide mounting in the distributor.

12 Claims, 19 Drawing Figures SHEET 3 BF 3 PATENTEBUBI 16 I975 The invention relates to electrical contact breaker apparatus for spark ignition internal combustion engines and has for its object to provide an improvement therein.

The electrical contact breaker apparatus with which spark ignition internal combustion engines have hitherto been provided have required regular very careful positioning entailing the use of feeler gauges (to ensure the contact points opening exactly the required distance as the engine operates) before being clamped tightly in position by screws. This is because the contact points become pitted and worn after a certain period of use, due to sparking which occurs between the points, and so need to be replaced from time to time. If the engine should get very wet it is sometimes also necessary to remove the contact breaker apparatus so that the contact points can be dried out. After every removal, the contact breake'r apparatus has had to be reassembled with care and this has required time and a certain degree of skill. The object of the present invention is at least to simplify the operation to some extent.

According to one aspect of the invention, there is provided electrical contact breaker apparatus for a spark ignition internal combustion engine, the apparatus including a replaceable cartridge incorporating a set of electrical contact points, means whereby said cartridge can be slide mounted in position in an electrical distributor, and electrical contact means for establishing the required electrical connections to said contact points. The electrical contact means will preferably be such that the required electrical connections will be established as the cartridge is slide mounted in position. The replaceable cartridge will preferably be provided with an extension piece or loop of cord or the like which can be used to facilitate its insertion into or withdrawal from the distributor. A follower member for contacting a cam rotatably mounted in the distributor will preferably be provided as part of thereplaceable cartridge including the set of electrical contact points. Said cartridge will preferably be of tapered form to facilitate its location in the required position in similarly tapered guides or in a similarly tapered housing in the distributor, and may be provided with means for sealing an aperture in a distributor cap through which it is to be passed to take up its slide mounted position. Spring means for urging said contact points one towards the other may be provided as part of the replaceable cartridge or may alternatively be provided as a permanent part of the distributor, in which case the arrangement will be such that a movable one of said contact points will be engageable with said spring means as the car-- tridge is slide mounted in position.

According to another aspect of the invention, there is provided, in combination, a replaceable cartridge incorporating a set of electrical contact points, and a housing, or a mounting plate provided with guides, in which said cartridge can be slide mounted to take up a required position, electrical contact means being provided for establishing the required electrical connections to said contact points, and said housing or mounting'plate being capable of being mounted in an electrical distributor in a carefully adjusted position. The electrical contact means will preferably be such that the required electrical connections are established automatically as the cartridge is slide mounted in position in the housing The replaceable cartridge may be provided with an extension piece or loop of cord or the like which will project outside the housing or beyond the guides in the mounting plate so that it can be used to facilitate the insertion of the cartridge into or with drawal from said housing or mounting plate. It may also be provided with means for sealing an aperture in a distributor cap through which it is to be passed to take up its required position in the housing. A follower for contacting a cam rotatably mounted in the distributor will preferably be provided as part of the replaceable cartridge. Preferably, also, said cartridge will be of tapered form and the housing therefor or guides, as the case may be, will be similarly tapered to facilitate the location of the cartridge at a required position in said housing or on the mounting plate so that the cam follower will be in turn located in a pre-ordained position relative to the cam to ensure that the contact points open the required distance and at the instant of time required. A suitable housing for the cartridge may be conveniently be at least in part moulded of a synthetic plastics material. Alternatively, it may be made from metal plate suitably pressed into the required shape. The housing or mounting plate, as the case may be, may be provided with screw holes of the same size and spacing as mounting plates of conventional replaceable contact breaker apparatus to facilitate the substitution thereof.

According to a further aspect of the invention, there is provided an electrical distributor having a cam rotatable at its axis and a replaceable cartridge, incorporating a set of electrical contact points, slide mounted so as to be located at a required position relative to said cam, electrical contact means being provided which have established the required electrical connections to said contact points. The electrical contact means will preferably be such that the required electrical connections have been established as the cartridge has been slide mounted in position. A follower member, contacting said cam for opening and closing the electrical contact points, may form part of the replaceable cartridge. The replaceable cartridge may be of tapered form and in this case the distributor will be provided with similarly tapered guides or with a similarly tapered housing for the reception of said cartridge. A suitable housing for the cartridge may be constituted by or include a synthetic plastics moulded construction. Alternatively, it may have been made from metal plate suitably pressed into the required shape. The distributor cap will preferably be provided with anaperture through which a cartridge having a worn set of electrical contact points may be withdrawn and a replacement set in a replacement cartridge can be inserted. In this case,

' the replaceable cartridge may be provided with means for sealing said aperture when the cartridge has been slide mounted in its required position. Alternatively, a closure cap may be provided to close said aperture during normal service, the closure cap preferably conforming to the curvature of the distributor cap and being pivotally connected thereto or being retained in position by resilient means. If the replaceable cartridge is provided with an extension piece capable of being used as a handle to facilitate its insertion into or withdrawal from the distributor, such a closure cap will be such as to allow for movements of the extension piece as advance" movements of the electrical contact points and cam follower occur as engine speed increases.

According to another aspect of the invention, there is provided a method of making a replaceable cartridge as described above, the method including the steps of moulding a body part therefor in a mouldable material and subsequently fitting the electrical contact points and the follower member therein. The mouldable material will preferably be a synthetic plastics material.

Preferably also, the arrangement will be such that a root end of the resilient metallic strip which carries one 'of the contact points and a root end of a resilient leaf I embodying the invention,

FIG. 2 is a sectional view on the'line 2-2 in FIG. 1,

FIG. 3 is a sectional view on the line 33 in FIG. 1, FIG. 4 is a sectional view on the line 4-4 in FIG. 1, and

'FIGS. 5 to 19 are views which will presently be referred to in connection with possible modifications of the apparatus. I

Referring now to FIGS. l to 4 of the drawings, an electrical distributor for a spark ignition internal combustion' engine has a cam rotatable atits axis within a body 12, a follower member 14 contacting said cam for opening and closing electrical contact points 16, 18 and a rotor arm 20 mounted on the upper end of a drive shaft 22 on which the cam is formed. The rotor arm is capable of being mounted on said drive shaft in only one position and is provided with a resilient contact piece 24 which contacts acontact terminal 26 within a cap 28. Said cap can be mounted on the body of the distributor, in register therewith, and retained in position by means of a pair of clips '30, so that a metallic peripheral edge portion 32 of the rotor arm electrically contacts in turn a number of metal contacts 34 within the distributor to transmit an electric current to each of the sparking plugs (not shown) of the engine .in the required sequence through the plug leads 36. A condenser 38 is also mounted within the distributor cap.

The contact points 16, 18 and the follower member 14 areincorporated in a replacement cartridge generally indicated 40 in FIG. 1. Said cartridge has a metal base plate 42 with upstanding lugs 44 and 46 at its opposite ends. The lug 44 carries the contact point '16 whereas the lug 46 secures one end of a resilient metallic strip 48 although it is electrically insulated there-.

from by means of a non-conducting element 50 in the form of a washer and integral bush. The contact point 18 is carried at a free end of the metallic strip and the arrangement is such that, until acted upon by the lobes of the cam 10 through the follower 14, the metallic strip holds the contact point 18 firmly in contact with the contact point 16. A resilient metallic contact 52 is also carried by the lug 46 and is electrically connected to the resilient metallic strip 48. The follower member 14 is made of a synthetic plastics material and is moulded integrally with a resilient leaf element 54 a thickened end of which remote from the follower member is carried by the upstanding lug 46. A screw 56 extends through the upstanding lug and the several elements connected to it.

The various elements incorporated in the replaceable cartridge 40 are encased at one end in a mass of synthetic plastics material 58 which has been moulded around them. The cartridge is generally of wedge shape, tapered as shown in both longitudinal planes, but the underside of the metal base plate 42 is left exposed and the resilient metallic contact 52 projects somewhat from one side face of thecartridge. In addition it will be observed that the follower member 14 projects from the opposite side face of the cartridge and sufficient space has been left around the greater length of the resilient metallic strip 48 and the leaf element 54 to allow the contact points 16, 18 to be opened and closed normally when the follower is acted upon by the cam 10. An extension piece 59 in the form of a slender stalk is secured to the replaceable cartridge and serves as a handle therefor.

Means are provided whereby the replaceable cartridge 40 can be slide mounted in position in the distributor to take up a required position relative to the cam, that is to say, a position in which the follower 14 is located in such a position that the electrical contact points 16, 18 are opened by the correct amount and at precisely the correct instant of time as the cam rotates. These means take the form of a housing, generally indicated 60 in FIG. 1, which is provided with a metallic mounting plate 62 having screw holes 64 for the reception of securing screws 66. The screw holes are of slightly elongate form as shown and are of the same size and are disposed at the same spacing as those of mounting plates of conventional replaceable contact breaker sets to facilitate the substitution thereof.

Upstanding side walls 68, and a top piece 72 all made of a synthetic plastics material form part of said housing and define an aperture for the reception of the. replaceable cartridge, the aperture being similarly tapered of course and the arrangement being such that the cartridge can be placed therein with a small degree of stick, that is to say, it can quite easily be extracted even after long use. A side portion of the housing is shown to have cutaway at 74 so that when the replaceable cartridge has been inserted the follower member 14 projects therethrough and clearance is provided for the rotation of a cam. Clearance is also provided for the cylindrical body part of the rotor arm 20 which closely overlies the follower member. A resilient metallic contact member 76 projects through the wall 70 of the housing and is arranged to abut against the contact 52 when the replaceable cartridge is slide mounted in position. The contact member 76 is connected to a metal plate 78 on the body to which electric leads (not shown) can be connected so that they are electrically connected to the contact point 18. The mounting plate 62 of the housing is automatically connected to the contact point 16 as the replaceable cartridge is slid into position in the housing by virtue of the fact that the metal base plate 42 of said cartridge immediately overlies the mounting plate. A hole is provided in the top piece 72 of the housing at its narrower end and is provided' so that, when the contact breaker apparatus is first being fitted in position in the distributor, a feeler gauge (not shown) can be inserted therethrough to measure the opening of the points of the replaceable cartridge as the housing is fixed permanently in the required position. Thereafter, the housing will never need re-adjustment and a new cartridge will always find its proper position relative to the cam without subsequent use of a feeler gauge.

A worn cartridge can be withdrawn from the housing 60 for replacement by a new cartridge through an aperture 80 in the wall of the distributor cap, a removable closure member 82 being provided to close said aperture during normal service. The closure member conforms to the curvature of the distributor cap and is provided with a sponge rubber sealing strip 81 around its edges to prevent the ingress of moisture and dirt. It is retained in position on the distributor cap by means of a length of strong elastic 83. The aperture 80 is in line with the cartridge and housing. When the engine is running, automatic speed responsive advance mechanism (not shown) forming part of the electrical distributor will move the cartridge and its housing relative to the distributor body and cap but this is of no consequence because it will be only a very small movement. The maximum Advance of most spark ignition internal combustion engines is in the region of to 12 so that it will be seen that the amount of movement is very small and is largely a movement longitudinal of the cartridge and housing, the more so if the axis about which the automatic advance movements take place is not co-incident with the axis of the cam but is positioned towards that side of the distributor remote from the cartridge and housing therefor. The depth of the removable closure member 82 however will be made sufficient to allow for this movement.

It will of course be understood that if the existing setting of the contact breaker points is to be maintained, it is important that a replacement cartridge must be identical in all material respects to that of a cartridge which it is to replace in order that its follower member will automatically take up a required position relative to the distributor cam as the replacement cartridge is slide mounted in position. That is to say, the outline configuration of each must be the same in all material respects and their follower members must project the same distances from their side surfaces and must have the same longitudinal positions also. On the other hand however, it will be understood that if a different setting of the contact breaker points is required, for example to suit varying atmospheric conditions, a replacement cartridge may be appropriately different from the cartridge which it is to replace. If they are to be of tapered form, the precise angle required for the replacement cartridge and housing therefor may be determined by trial and experiment and will be dependent on the materials of which the two are made because it will be understood that a non-stick taper or a very small degree of stick is preferred so that the cartridge can easily be extracted even after long use. Furthermore, if

the included angle of taper is not sufficiently great it will be possible for the longitudinal positioning of the cam follower member to vary according to how hard the cartridge is pressed into its housing, and this will not be desirable. On the other hand, if the included angle of taper is too great, it will be found that the cartridge is quite loosely mounted in the housing and positive means may be required to retain it in position. (The resilient contact 52 helps to maintain it in position of course and the cam rotates in an anti-clockwise sense which in the example illustrated tends to maintain the cartridge in position). An included angle of taper in the region of 10 has been found suitable in the experimental cartridge and housing illustrated, but it is thought that a range of included angles within the range of 50 to 20 would be suitable if stick due to friction is to be relied on to retain the cartridge in position.

Thus there is provided an electrical distributor, for a spark ignition internal combustion engine, which can be fitted with replacement contact points in a minimum of time and with none of the trouble and inconvenience involved when fitting replacement contact points in distributors employed hitherto, that is to say, the trouble and inconvenience of setting the points with the aid of a feeler gauge is eliminated, when once the guide plate or housing for the replacement cartridge has been carefully secured in the correct position. Furthermore, there is no danger of losing the screws with which conventional electrical contact points are secured in position. It will also be understood that if replacement contact points can be fitted without even removing the distributor cap, this allows the designer of a spark ignition engine greater freedom in positioning the distributor and other ancillary equipment. For example, it is no longer wholly impractical to locate the distributor in such a position that other equipment, for example the air cleaner unit, must be removed before the distributor cap can be removed. In a distributor embodying the present invention, the cap will only require to be removed at very long intervals of time. A further advantage is that since the fitting of replacement contact points is such a very simple matter in an electrical distributor embodying the invention, a breakdown due to water entering the engine compartment and wetting the points can quickly be cured by removing the points and drying them before replacing them or by fitting a replacement set of points (although in fact it may be found that since the points are to some extent shrouded by the housing, the apperatus is not as prone to this trouble as contact breaker apparatus used hitherto).

Referring now to FIGS. 5 and 6, an alternative method of forming a suitable housing for a replaceable cartridge as described above entails stamping the shape shown in FIG. 5, from a single metal plate generally indicated 84, and pressing it into the shape shown in FIG. 6 by folding along the chain-dotted lines. An apertured tab is set from the area of the plate which is to form a side wall of the housing for the electrically insulated mounting of an electrical contact against which the resilient contact 52 of the replaceable cartridge is to abut as the cartridge is slide mounted in position. The electrical contact carried by the apertured tab may be the head of a small screw 88 electrically insulated from the tab by fibre washers 90 one of which has an integral bush 91 and retained in position by nuts 93. The portions of the metal plate which are to constitute the other side wall of the housing need not be joined to the portion which is to constitute the mounting plate and in fact can be spaced therefrom as shown in FIG. 6.

Turning now to FIG. 7, this illustrates an alternative form of replaceable cartridge incorporating a set of electrical contact points. In this alternative form of cartridge, the various elements incorporated in it have not been encased in a mass of synthetic plastics material. Instead, the metal base plate 42 has been provided with upstanding lug portions 92 and 94 in addition to the lugs 44 and 46 which carry the contact points, the metallic contact 52 and the cam follower. The four lug portions are arranged in such a way that they define the same outline shape as thatof the cartridge previously described, that is to say, tapered in two planes, so that the cartridges are thus interchangeable. An extension piece 96 is formed integrally with the base plate 42 to serve as a. handle. 1

ln FIGS. 8 and 9there is illustrateda further form of replaceable cartridge incorporating a set of electrical contactpoints which in some ways is similar to that illustrated in FIG. 7 in the sense that the various elements incorporated in the cartridge have not been encased in a mass of synthetic plastics material. In this case a metal shell 98 of said cartridge is of generally channel shape, tapering as shown in both planes, and at its narrower end the channel section has been upset to provide a convenient mounting for the contact point 16. The resilient metallic strip 48 which carries the contact point 18 is secured at one end within the wider end of the channel section of the shell by means of a rivet 100, means being provided to ensure that the resilient strip and said rivet are electrically insulated from the shell. (A loop of cord 102 is shown to be secured by the rivet to the cartridge for the purpose of providing convenient means by which the cartridge can be extracted from its housing. Also it will be seen that the headof the rivet projects somewhat beyond the external surface of the shell so that it can engage a resilient contact forming part of the housing in which the cartridge is to be slide mounted. However, these are mere details and in these respects the cartridge could quite well be the same as that previously described with reference to FIG. 7,).

The leaf element 54 with which the follower member 14 is integrally moulded in'a synthetic plastic material is in this case not secured in position by the means which secure the fixed end of the resilient metallic strip 48. Instead, the end of said leaf element remote from the follower member is formed with a root element 104 provided with parallel tab portions 106 which are received in guides 108 in the parallel flanges of the channel'section of the shell. This form of connection of the follower member lends itself ideally to the concept of having a plurality of such follower members of varying widths available for selective fitment according to the setting of the spark gap required and/or with various lengths of leaf element according to an advance or retard adjustment which it is required to make.

cated 109 and a spring steel element 110 and a synthetic plastics element 112 which can simply be slotted in position as best shown in FIG. 10. The spring steel element 110 incorporates the resilient metallic strip 48,

which carries the contact 18, and an integral resilient metallic contact member 52. What is in effect the root end of the metallic strip 48 is provided with a Vee portion 114 for engaging a similarly shaped notch 116 in the body part. A major length of the contact member 52 is arranged to extend along a narrow slot 117 formed in a side face of the body part.

The synthetic'plastics element 112 on the other hand incorporates the resilient leaf element 54, carrying the follower member 14, and also an integral handle part 118 by means of which the cartridge can be inserted into position in its housing or extracted therefrom. A

portion of the element between the resilient leaf and the handle part is provided with a projection 120 which is arranged to slide into engagement with the Vee portion 114 of the spring steel element 1 l and with a projection 122 on its opposite face arranged to slide into engagement with a slot 124 in the body part. The electrical contact point 16 has been formed with a spigot portion 126 which has been press fitted in a hole formed in the pre-moulded body part. Said spigot portion projects very slightly proud of the side of the body part and is arranged to abut against a suitable electrical contact of a housing in which the cartridge is to befitted (for example the metal side wall of the housing which has been described with reference to FIGS. 5 and 6).

This form of cartridge also lends itself to the quick and easy replacement of its follower member by another such follower member having a slightly greater or lesser width and/or having a slightly longer or shorter leaf element.

Referring now to FIG. 12, this illustrates a form of housing for a replaceable cartridge as described above (particularly but not exclusively for the kind of cartridge described with reference to FIGS. 11 and 12) the housing having been designed with simplicity and ease of manufacture very much in mind.

The housing is made in two parts; a synthetic plastics part 128 and a metallic basal part 130 connected to gether by screws 129 which are to secure the housing in position in a distributor. The synthetic plastics part has been moulded with a tapering slot 132 extending across its underside as shown for the reception of the replaceable cartridge, and with an electrical contact 134 projecting through a side wall for the engagement of one of the electrical contacts of the cartridge. The basal part 130 on the other hand is provided with an upstanding resilient lug 136 for the engagement of the other electrical contact of the cartridge. (It will however be realised that if the cartridge has a metal base to which its electrical contact point 16- is electrically connected, or a downwardly projecting electrical contact, the metallic basal part 130 may not be necessary). Referring now to FIG. 13, this is an exploded view similar to FIG. 1 and like reference figures indicate like parts. This arrangement does however incorporate various improvements. For example, the cartridge-40 is of a simplified form and includes a body part 138 made of a synthetic plastics material and having a generally channel shaped cross section as best shown in FIGS. 14 and 15, tapering as shown in both longitudinal planes. The root end of the resilient leaf element 54, on which the follower member 14 is formed, the root end of the resilient metallic strip 48 and the resilient contact 52 are riveted in the wider end of the body part by means of a rivet 140. A loop of cord 142 is also secured at the wider end of the cartridge to facilitate the extraction of the cartridge from the housing. The contact point 16 has been moulded in position at the narrower end of the body part and projects through the side wall of the body part to constitute an electrical contact at 144. The follower member 14 projects through an aperture in the side wall of the body part of the cartridge.

In FIGS. 16 and 17 there is illustrated a modification of the replaceable cartridge just described wherein the body part 138 has been moulded in a synthetic plastics material integrally with the follower member 14 and resilient leaf element 54. It will be seen that this construction of replaceable cartridge is extremely simple and includes the very minimum of separate parts. Consequently, it can be produced in quantity at a very low cost.

The housing 60 illustrated in FIG. 13 for the replaceable cartridge has been formed substantially as previously described with reference to FIGS. and 6, that is to say, from a single sheet of metal plate. The metal plate has been suitably pressed into the required shape shown in FIGS. 13 and 18 from the blank form shown in FIG. 19. However, in this case the screw 88, the head of which is to constitute an electrical contact for the resilient contact 52 of the replaceable cartridge, extends through a hole 146 in the plain side wall of the housing, and a positive stop 148 is provided for the abutment of the end of a replaceable cartridge being fitted in the housing. The arrangement is such that the side walls of the housing are sprung apart very slightly as the cartridge is being slide mounted in position, so that said cartridge will be retained in position by friction, an electrical connection simultaneously being established between the contact 144 and the housing, and the positive stop ensures the correct location of the cartridge irrespective of the manual pressure with which it is pressed into the housing.

A further improvement which has been incorporated in the arrangement illustrated in FIG. 13 resides in the fact that a removable closure member for the aperture 80 in the wall of the distributor cap is constituted by a plate member 150 conforming to the curvature of the distributor cap and secured at one end of a spring steel clip 152 which extends almost completely around the cap. A pad of sponge rubber 154 is secured by an adhesive at the inner curved surface of the plate member and is arranged to register in the aperture 80 for the purpose of excluding water and dirt. (The substitution of the loop of cord 142 for the extension piece 59 of the replaceable cartridge has rendered unnecessary the hollow form of closure member shown in FIG. 1). The closure member is of course shown in a position displaced away from the distributor cap in FIG. 13.

Various other modifications may be made without departing from the scope of the invention. For example, although it is obviously highly desirable that the electrical contact means should be such that the required electrical connections will be established automatically as the cartridge is slide mounted in position in the housing, this is not absolutely essential and it will be understood that there may well be at least one electrical lead which requires separate connection and disconnection. However, when the required electrical connections are established automatically, it may be found desirable to include a resilient metallic contact also between the base of the cartridge and the mounting plate of the housing or the surface on which the housing is fixed as the case may be. Furthermore, the replaceable cartridge need not necessarily be tapered in two planes or indeed be of tapered form. It could for example be mounted in parallel guides, but of course in this case it would need to abut against a positive stop when in the required position relative to the cam and would be retained by a resilient clip or the like. It will of course be realized that the replaceable cartridge need not necessarily be totally encased in the housing in which it is mounted as in the examples illustrated. For example, the base of the replaceable cartridge could have a dovetailed cross section and the mounting plate 62 would then need only to be provided with the complementary dove-tailed guides in which the base plate of the cartridge could be slide mounted. Consequently in this case the cartridge would not need to be encased in a mass of synthetic plastics material or be provided with lug portions designed solely to give the required outline shape. The replaceable cartridge could be provided with means for sealing an aperture in the distributor cap through which it is to be passed to take up its slide mounted position. However, the distributor cap need not necessarily be provided with such an aperture. As is customary at present, the distributor cap may be removable for the fitment of new contact points but the operation will still be facilitated by the fact that the use of a feeler gauge will not be required and screws will not need to be removed and then replaced when once the housing or mounting plate for the replaceable cartridge has been carefully located in the required position.

A replaceable cartridge may have what can be regarded as a standard points opening when the cam follower member is moved into line with the side face of the cartridge from which it normally projects. How-.

ever,- if desired, it may be provided with means whereby the opening may be varied to allow adjustments to be made, for example if the points are too smoothed after some use or to suit the requirements of a particular make of engine. Such variations may, for example, be effected in the case of the cartridges illustrated in FIGS. 7 and 8 by bending the lug 44 which carries the contact point 16 or in other cases by special shims being placed between the heel of the cam follower member and the resilient metallic strip 48 which carries the contact point 18.

I claim:

1. In an electrical distributor for an internal combustion engine having a cam rotated about a fixed axis, a replaceable contact carrying cartridge that comprises a body, a fixed electrical contact on said body, an electrically conductive member movably mounted on said body and having a movable electrical contact thereon, spring means acting on said member for resiliently urging said movable contact toward engagement with said fixed contact, and a cam follower movably mounted on said body bearing against said movable member; and means for operatively mounting said cartridge in the distributor for locating said cam follower in predetermined association with the cam comprising a housing within which said cartridge is removably received in predetermined position therein with said cam follower in operative engagement with said cam, and means for adjustably fixing said housing in a position wherein said cam and cam follower are so related that during rotation said cam causes a predetermined degree of periodic separation of said contacts.

2. In the electrical distributor defined in claim 1, said cartridge being slidably mounted to assume said predetermined position in said housing.

3. In the electrical distributor defined in claim 2, said body being substantially tapered and being fitted into a correspondingly tapered part of said housing.

4. In the electrical distributor defined in claim 1, said means for mounting the cartridge in said housing comprising location surfaces on said housing and against which said body is adapted to bear, said location surfaces lying in a plane parallel to a plane tangential to said camp so that said adjustable positioning of said housing relative to said cameffectively determines the extent of opening movement of the electrical contact points as said cam rotates, and stop means for locating said body of the replaceable cartridge in operative engagement with said location surfaces of said housing.

5. An electrical distributor as defined in claim 4, wherein said stop means is constituted by a positive stop forming a part of the housing and against which said body of said replaceable cartridge abuts when inserted into the housing.

6. An electrical distributor as defined in claim 4, wherein said stop means is constituted by said body part of said replaceable cartridge forming a wedge-like configuration and said location surfaces of said housing being similarly formed.

7. An electrical distributoras defined in claim 1, wherein said member is a metallic spring strip carrying said movable contact and constitutes said spring means. a

8. An electrical distributor as defined in claim 1, wherein said housing is metal and electrical connection is established between said fixed electrical contact of said replaceable cartridge and said housing as said replaceable cartridge is received in said housing.

9. An electrical distributor as defined in claim 8, wherein an electrical contact element is carried by said replaceable cartridge and is electrically connected to said movable contact, and a metallic contact element is carried by but electrically insulated from, said housing, said electrical contact element of said replaceable cartridge being brought into resilient contact with said electrical contact element of said housing as said replaceable cartridge is received in said housing.

10. A replaceable contact carrying cartridge for an electrical distributor comprising a body of wedge-like external configuration adapting it for slide mounting in the distributor, a fixed electrical contact on said body, a metallic strip carrying a movable contact adapted'for movement into and out of engagement with said fixed other end fixed on the body.

Claims

4. In the electrical distributor defined in claim 1, said means for mounting the cartridge in said housing comprising location surfaces on said housing and against which said body is adapted to bear, said location surfaces lying in a plane parallel to a plane tangential to said cam so that said adjustable positioning of said housing relative to said cam effectively determines the extent of opening movement of the electrical contact points as said cam rotates, and stop means for locating said body of the replaceable cartridge in operative engagement with said location surfaces of said housing.

7. An electrical distributor as defined in claim 1, wherein said member is a metallic spring strip carrying said movable contact and constitutes said spring means.

9. An electrical distributor as defined in claim 8, wherein an electrical contact element is carried by said replaceable cartridge and is electrically connected to said movable contact, and a metallic contact element is carried by but electrically insulated from said housing, said electrical contact element of said replaceable cartridge being brought into resilient contact with said electrical contact element of said housing as said replaceable cartridge is received in said housing.

10. A replaceable contact carrying cartridge for an electrical distributor comprising a body of wedge-like external configuration adapting it for slide mounting in the distributor, a fixed electrical contact on said body, a metallic strip carrying a movable contact adapted for movement into and out of engagement with said fixed electrical contact, spring means for biasing said movable contact toward engagement with said fixed contact, and a cam follower mounted for movement on said body bearing against said metallic strip.

11. The cartridge defined in claim 10, wherein said strip is a spring metal strip fixed at one end in the body and mounting said movable contact on the other end.

12. The cartridge defined in claim 11, wherein said cam follower comprises a cam engaging terminal mounted on the free end of a flexible leaf having its other end fixed on the body.