GB2113325A - Locking spindle for printing wheels - Google Patents

Abstract

A locking spindle for printing wheels for printing apparatus which wheels are arranged side by side and are movable particularly by rotation to the appropriate position, for e.g. stamping, is made of plastics material and has bores 4 for spring-urged locking elements, preferably in the form of balls 3, in which these locking elements can be inserted and held in place by means of projections 7 provided at the outer ends of the bores 4. Each projection forms an undercut 7 and is integrally formed with the locking spindle 1. During assembly, the springs 2 and balls 3 are inserted into the bores 4 from outside, whilst the projections are deformed somewhat to allow the balls to enter. The projections are, as shown, annular having a frusto-conical surface with more than one-third of the ball projecting beyond the contour of the locking spindle. <IMAGE>

Description

SPECIFICATION Locking spindle for printing wheels The invention relates to a locking spindle for printing wheels or the like which are arranged side by side, are movabie particularly by rotation and engage in the appropriate position, for paginating, numbering, stamping, price marking and printing equipment or the like, wherein, on the locking spindle for the movable printing wheels, there are provided locking balls, pins or the like projecting radially out of the contour of the spindle and pressed outwards by a spring, and on the printing wheels there is provided, for each number or character, a stop recess adapted thereto, and on the bore receiving the spring and the ball or the like there is provided a detent for engaging over the maximum diameter of the ball or the like.

It is known to use spring-loaded ball- or pintype arrangements with spherically shaped tips as locking devices for printing wheels.

These locking elements are inserted with the spring into the corresponding recess or channel in the locking spindle, and then a detent constriction in the form of an undercut has to be provided at the exit there from. This is understandably difficult, since the locking elements inserted have to be pressed down counter to the force of the spring and furthermore these parts have to be very precise and, after the fixing of the element forming the constriction, all the locking elements have to project as uniformly as possible out of the locking spindle.

The aim is therefore to provide a locking spindle of the kind mentioned above in which manufacture and assembly is simplified.

This aim is achieved essentially by the fact that the locking spindle consists of plastics material and the projection or the like forming the undercut for retaining the ball or the like is an integral part of the locking spindle. This does away with the need for subsequent provision of a constriction on the locking spindle, with the consequent risks of inaccuracy. Instead, the retaining projection or the like may be precisely formed at the same time as the locking spindle itself is made.

This surprising and apparently paradoxical solution provides a process for the production of a locking spindle with locking balls inserted therein, wherein a locking spindle having holes or channels extending at right-angles thereto for receiving the balls or the like is injection-moulded or cast with integral retaining projections for the balls or the like and then the spring is inserted and the ball is pushed through the entrance, which is narrower than its own diameter, into its channel.

In fact, tests have shown that, with a prefabricated integral undercut provided on a plastics locking spindle, the balls can be pushed through this constriction with a certain amount of force, and then the somewhat resilient material engages over the balls at the desired height and holds them in position counter to the force of the springs which are inserted at the same time. This avoids the laborious and complicated procedure of subsequently providing constrictions or undercuts when the springs and balls have already been inserted. Accordingly, there is no longer any need for special production of very small components which hitherto were subsequently mounted at the end of the ball channels to form undercuts. The work involved in fitting these components is naturally also avoided.

Moreover, the complicated procedure for holding the balls in place whilst the constriction is provided is done away with.

Preferably, the projection which forms the undercut for the ball or the like runs in a circle around the upper edge of each channel.

The annular projection may have a slightly smaller diameter than the locking element, so that the ball or the like is held just above its maximum diameter. The locking element, more particularly a ball, then projects far enough out of the locking spindle but is still sufficiently firmly held and in addition the annular projection itself need be deformed only relatively slightly when the ball is pressed in during assembly.

The undercut on the inside for holding the ball or the like in position may have a surface shaped like a cone shell, the meridian lines of this surface forming an obtuse angle with those of the cylindrical surface of the bore or hole which receives the ball. In this way, the surface may be largely adapted to the shape of the contour of the ball somewhat above its maximum diameter.

Insertion of the ball by subsequently pushing it in is made easier if a depression or recess having substantially the same diameter as the ball or the hole which receives the ball is provided on the outside of the locking spindle above the retaining ring for the ball or the like which forms the undercut. The ring, which is frustum-shaped on the inside and forms the undercut or constriction, projects beyond the inner contour of the channel for the locking element in the manner of a lip and can be displaced correspondingly when the ball is pushed in; advantageously this deformation of the construction only has to occur once, namely when the ball or other locking element is brought into its operating position.

The surprising measure of providing a retaining element at the outset, which will prevent the locking element from passing through later when the apparatus is used, and of pushing the locking element through this retaining means, substantially simplifies the manufacture and assembly of the locking spindle.

In order that the invention may be readily understood an embodiment thereof will now be described by way of example with reference to the accompanying drawings in which Figure 1 shows a longitudinal section through a locking spindle according to the invention with locking elements, in this case in the form of balls, already inserted, Figure 2 shows, on a larger scale, a crosssection through the locking spindle in the region of a channel for receiving the ball, and Figure 3 is a view corresponding to Fig. 2, in which the ball is pressed down so that the constriction at the end of the ball-receiving channel is clearly visible.

A locking spindle, generally designated 1, serves to receive printing wheels (not shown in detail) which are rotatable relative to the locking spindle 1 and can be releasably fixed in predetermined positions. This fixing is effected by means of locking connections, for which purpose springs 2 and locking balls 3 are mounted inside bores 4 in the locking spindle 1. The springs 2 are supported inside the bores 4, which are preferably circular in cross-section, on a step 5. For reasons connected with the manufacturing operation, a narrower bore 6 is located below the step 5.

To avoid having to provide an annular weld after the balls 3 have been inserted, i.e.

having to provide constrictions at the top ends of the holes 4 to form an undercut, it is proposed according to the invention that the locking spindle 1 consist of plastics material and that a projection 7 forming the undercut for retaining the ball 3 be formed as an integral part of and with the locking spindle 1 (cf. Figs. 2 and 3). This projection 7 forming the undercut for the ball 3 may run in a circle around the upper edge 10 of each channel 4.

Fig. 2, in particular, but also Fig. 3, clearly show that the annular projection 7 is slightly smaller in diameter than the locking element, in this case the ball 3, so that this ball 3 is held just above its maximum diameter D. As a result, more than one-third of the ball projects beyond the contour of the locking spindle 1, as indicated by the measurement 8 in Fig. 2.

The projection 7 or the corresponding undercut has on the inside a frusto-conical surface shaped (Fig. 3), the meridian lines of this surface forming an obtuse angle with those of the cylindrical surface of the bore or hole 4 which receives the ball 3. The undercut thus abuts diagonally and tangentially on that part of the surface of the ball which is gripped by this undercut just above the maximum diameter D.

Fig. 3, in particular, shows that there is a depression 9 or recess having substantially the same diameter as the ball 3 or the bore 4 which receives the ball 3, on the outside of the locking spindle 1 above the retaining ring 7 for the ball 3 which forms the undercut.

The locking spindle described above permits rapid manufacture and assembly owing to the fact that, with its bores or channels 4 extending at right-angles thereto for receiving the balls 3, it is injection-moulded or cast integrally with the retaining projections 7 for the balls 3 or the like, and then the springs 2 can be inserted and the balls 3 can be pushed through the constricted entrance into their channel 4. Thus, there is no need for any special subsequent measures for fixing the locking elements after they have been inserted into the channels 4. Since the locking spindle 1 is made of plastics, the projection 7 is deflected accordingly when the ball 3 is pushed in but then returns to its original position, at least sufficiently to be able to act as a retaining means counter to the force of the spring 2. Tests have shown that this provides a very simple method of inserting the balls and at the same time simplifying the use thereof.

All the features and details of construction given in the description, abstract, claims and drawing may be essential to the invention both individually and in any desired combination with one another.

Claims (7)

1. A locking spindle for side by side arranged rotatable printing wheels or the like which are detentable in desired positions for paginating, numbering, stamping, price marking and printing equipment or the like, wherein, in the locking spindle for the movable printing wheels, there are provided bores in which are received locking balls, pins or the like projecting radially out of the contour of the spindle and urged outwardly by a spring, and on the printing wheels there is provided, for each number or character, a stop recess corresponding thereto, and in each bore receiving the spring and the ball or the like there is provided an detenting undercut for engaging over the maximum diameter of the ball or the like, wherein the locking spindle consists of plastics material and and inward projection or the like forming the undercut for retaining each ball or the like is an integral part of the locking spindle.

2. A locking spindle as claimed in claim 1, in which the projection forming the undercut for the ball runs in a circle around the outer end of each channel.

3. A locking spindle as claimed in claim 2, in which the annular projection has a slightly smaller diameter than the locking element, so that the ball or the like is held just above its maximum diameter.

4. A locking spindle as claimed in any of claims 1 to 3, in which the undercut has on the inside a frustoconical surface, the meridian lines of this surface forming an obtuse angle with those of the cylindrical surface of the ball receiving bore.

5. A locking spindle as claimed in claims 2, 3 or 4, in which on the outside of the locking spindle above the retaining ring for the ball or the like which forms the undercut, there is provided a depression or recess having substantially the same diameter as the ball or the bore which receives the ball.

6. A process for the production of a locking spindle of the kind mentioned in claim 4 with locking balls inserted therein, in which a locking spindle having holes or channels extending at right angles thereto, for receiving the balls or the like, is injection moulded or cast with one or more integral retaining projections for the balls or the like and then the spring is inserted and the ball is pushed through the constricted entrance into its channel.

7. A locking spindle for printing wheels or the like substantially as hereinbefore described with reference to the accompanying drawings.