EP2604557A2 - Pressing device with elastic spring elements - Google Patents

Abstract

The device has twin spring system and single spring system with brush elements (B-1-B-n) which are arranged opposing a base board (34) and provided with an initial pressure force (F1) based on thickness of mail item along transportation path. The pressure force of the brush elements is increased to minimum pressure force (F2) and increased pressure force (F3) with increasing thickness of the mail item, where the pressure forces are set satisfying a preset relationship. The stop elements (341) of base board are provided to limit stroke of base board to base plate (38).

Description

The invention relates to a pressure device with resilient elements, according to the type specified in the preamble of claim 1 and is applicable to all arrangements which use elastic pressure elements, which should not experience permanent deformation. In particular, the invention makes it possible to simplify a transport or printing device intended for use in a postage metering system or in a postage meter machine. When reference is made below to flat goods, this is not intended to exclude paper strips, mailpieces or other goods for which the counterpressure device is also suitable.

From the German Utility Model DE 20 2007 019 194 U1 a device for pressing flat goods to a transport module is known which uses a conveyor belt brush system. This system works well for mailpieces of sufficient thickness, such as for letters, even over a longer period of time. The pressure force is realized by an overstroke between the conveyor belt and brush elements with simultaneous movement of the conveyor belt. The brush elements have holders. The holders are mounted in a brush body. The latter is mounted in a recording medium. Another from the DE 20 2007 019 194 U1 Fig. 4 known prototype, has an aforementioned brush elements exhibiting first spring system and a second spring system, which is mechanically coupled to the first. The second spring system consists of a base plate which is resiliently mounted on standoffs on a bottom plate and opposite to the latter.

For pressing brush elements are used as spring elements that produce a non-linearly increasing pressure force F1. The second spring system presses with a linearly increasing pressure force F2 the recording medium with the brush elements against gravity against the conveyor belt. An overstroke is generated even when there is no flat good between the conveyor belt and the pressure device (idle state). The overstroke is designed so that even when occurring component tolerances of the pressure device in the resting state, a pressing force to the conveyor belt is certain to exist. The deflection of the pressure device takes place by spring force against gravity and is limited by limiting means on the overstroke of about 2 mm. The pressing force F2 is so great that at rest an overstress and thus a permanent deformation of the brush elements of the pressure device is caused, wherein the formula is: $$\mathrm{F}\mathrm{1}\mathrm{>}\mathrm{>}\mathrm{F}\mathrm{Second}$$

The spring force F1 is always lower in the idle state due to the material with the duration of the deformation, which leads to transport problems with very thin flat goods, especially for franking strips.

The object to be solved, to develop a pressure device with resilient elements, which is suitable for mail pieces of different thickness and over a long period without deformation of the brush elements secure transport especially very thin flat goods, especially franking strips guaranteed.

The object is achieved with the features of claim 1.

It has been found that the brush elements of a brush body, which form a first spring system, are particularly well suited to the transport of thin flat goods, when the brush elements are undeformed in the resting state of the pressure device.

A pressure device, which is equipped with resilient elements, in particular brush elements is mechanically coupled instead of a single-spring system with a double spring system, which provides both the necessary pressure and on the other hand optimizes the pressing force so that a permanent deformation of the brush elements in Hibernation of the pressure device is prevented. The brush elements are the resilient elements of a first spring system, which are deformed from a force that a minimum pressure force F1min of the first spring system equivalent. Their pressure force increases non-linearly with increasing thickness of the goods that are transported in the operating state of the conveyor belt along a transport path and get between the conveyor belt and the pressure device. It has been empirically determined that a permanent deformation of the brush elements is prevented at rest when the brush elements act on the conveyor belt with a lower pressure force than with a minimum pressure force F1 min of the first spring system. In the resting state of the pressure device, therefore, acts a second spring system with the pressing force F2 on the first spring system on the conveyor belt to absorb those forces that could deform the brush elements, wherein applies to the pressure forces: $$\mathrm{F}\mathrm{1}\min \mathrm{>}\mathrm{F}\mathrm{2}\min \mathrm{,}$$

The minimum pressure force F2 of the second spring system is chosen to be lower than the minimum pressure force F1min of the first spring system, so that it is ensured that the force acting at rest of the pressure device minimum pressure force F2 on the conveyor belt below the sum of the deformation forces D _{B *} of all brush elements B1 *, B2 *, ..., Bi *, ..., Bn * remains: $$\mathrm{F}\mathrm{2}\min \mathrm{<}\mathrm{F}\mathrm{1}\min \mathrm{=}{\mathrm{\Sigma D}}_{\mathrm{B}\mathrm{*}}\mathrm{=}{\mathrm{D}}_{\mathrm{B}\mathrm{1}\mathrm{*}}\mathrm{+}{\mathrm{D}}_{\mathrm{B}\mathrm{2}\mathrm{*}}\mathrm{+}\mathrm{...}\mathrm{+}{\mathrm{D}}_{\mathrm{Bi}\mathrm{*}}\mathrm{+}\mathrm{...}\mathrm{+}{\mathrm{D}}_{\mathrm{Bn}\mathrm{*}}$$

In the resting state of the pressure device no good in the transport path is present, in contrast to the operating condition. In operation, a flat good is transported. Due to the thickness of the flat material, there is a deflection of the recording medium in the direction of gravity. The deflection of the receiving carrier counteracts a spring force. The latter is limited by limiting means, which are arranged between the base plate and the base plate. Due to the limitation, the second spring system is biased. Furthermore, at least two first stop elements are provided, which limit the stroke of the base plate to the base plate in the direction of gravity. Due to a spring constant R2 of the spring force of all compression springs together, the pressing force F2 increases proportionally with the deflection. In the deflection, a path is covered, which is limited by the stop elements. The aforementioned way corresponds to an average thickness of the flat material (mail piece). This path is called a hub.

If initially individual brush elements are deformed upon arrival of the edge of a flat material and during its transport, then transmits the deflection in the sequence as a whole to the deflection of Recording medium up to a predetermined stroke of s ₁ = 2 mm. The pressure force F2 of the second spring system is lower overall than the minimum pressure force F1min of the first spring system. In the mechanical coupling of the two spring systems no deformation of the brush elements occurs at rest, as long as the pressure force remains below the sum of the total deformation forces Σ D _{B *} . Up to a stroke of the recording medium in the direction of gravity corresponding to a first thickness of a flat material, for example a mail piece of up to 2 mm, only the pressing force F2 of the second spring system on the mail piece is effective. At the stroke s ₁ = 2 mm of the recording medium in the direction of gravity corresponding to the first thickness of a mail item, the first stop of the arrangement is reached, which limits the stroke that can occur between the base plate and the base plate of the pressure device. Due to the limitation of the stroke, the pressing force F1 of the first spring system acts instead of the pressing force F2 of the second spring system. The pressing force F1 increases due to the deformation of the brush elements from the minimum pressing force F1 min non-linear with the thickness of the flat material, as long as the minimum pressing force F3min of a further third spring system is not reached. Also, mail pieces of medium thickness can be transported in the operating state, without a permanent deformation of the brush elements occurs, as long as a pressing force of the first spring system is not exceeded, in which the reversible deformation passes into an irreversible deformation. It occurs in the brush elements used in the embodiment at the first thickness of a flat material. The further increase of the pressing force with the thickness of the flat material is limited at a second thickness of the flat material. At this second thickness, an optimal pressure force F1opt was determined empirically.

In the operating state of the pressure device for postal items from the second thickness another spring system is effective, which acts with a minimum pressure force F3min = F1opt when the optimum pressure force F1opt of the first spring system is achieved. The pressure force continues to increase linearly with the thickness of the flat material as of F3min. The proportionality factor is called the spring constant R3 and is much larger than the spring constant R2.

This results in a mechanically coupled double-spring system which acts on the brush body. This can be used to transport thin to thick flat goods (mail pieces), whereby the following applies to the pressure forces: $$\mathrm{F}\mathrm{3}\mathrm{>}\mathrm{F}\mathrm{3}\min \mathrm{=}\mathrm{F}\mathrm{1}\mathrm{opt}\mathrm{>}\mathrm{F}\mathrm{1}\mathrm{>}\mathrm{F}\mathrm{1}\min \mathrm{=}\mathrm{F}\mathrm{2}\mathrm{Max}\mathrm{>}\mathrm{F}\mathrm{2}\mathrm{>}\mathrm{F}\mathrm{2}\min \mathrm{,}$$

Each of the brush elements Bi * consists of a bundle of brush hairs or bristles and has in the pressure force / thickness diagram on a nonlinearity of the deformation force D _{Bi *} , which is based on the increasing friction of the brush hair or bristles with each other in their deformation the friction increases with their deformation. In the case of the optimum pressing force F1opt, brush elements are briefly deformed in the operating state of the pressure device, but without the deformation being irreversible. Rather, the deformation is still reversible.

Advantageous developments of the invention are characterized in the subclaims or are presented in more detail below together with the description of the preferred embodiment of the invention with reference to FIGS.

In the Fig. 1 is a front view of the pressure device in the operating state shown as a schematic diagram. A white arrow points in the transport direction of a flat material 4. The brush body has the brush elements B * = B1 *, B2 *, ..., Bi *, ..., Bn *. The brush elements B1 * and B2 * are chamfered to facilitate the entry of especially a thicker material in the gap between the conveyor belt 2 and the pressure device. The receiving carrier 32 * (brush body) is mechanically coupled to a double-spring system. The double spring system consists of the already known spring elements 37 *, which are arranged between a base plate 34 * and a base plate 38 *, which previously served to press the brush elements to a conveyor belt 2 and which in sum have a spring constant R2 and from further spring elements 42 *, which are arranged between the base plate 38 * and the chassis 40 * and in the sum have a spring constant R3. However, the spring constant R2 of the spring elements 37 * is now chosen to be much lower than in the previous solution according to DE 20 2007 019 194 U1 , so that it is ensured that in the resting state of the printing device, the pressing forces below the deformation force of the brush elements B * remain. The spring system is now softened with the spring elements 37 *, as the first spring system with the brush elements B * or the further third spring system with the spring elements 42 *.

The FIG. 1 shows that the base plate 34 * has been deflected in the direction of gravity. The deflection of the base plate 34 * counteracts a spring force, which is applied by at least two compression springs 37 *. The aforementioned spring force is limited by limiting means, consisting for example each of a lock washer 36 * and standoffs 35 *, wherein the base plate 34 * has an opening for passage of the spacer bolt 35 *. Due to the limitation, the second spring system is biased. The spring elements 37 * were compressed according to the thickness of the flat material 4, so that the locking washer 36 * and the base plate 34 * are spaced from each other.

At least two stop elements 341 * are mounted on the base plate 34 * and shaped to limit the stroke in the direction of gravity so that a stop on the base plate 38 * is achieved when the thickness of the flat material 4 - in the manner shown - a first thickness reached or exceeded.

At least two limiting elements 41 * are arranged on the chassis 40 * and limit the movement of the base plate 38 * in the resting state of the pressure device and in - in the FIG. 1 illustrated - operating state for thin flat goods. Thus, the effect of the other spring system against the direction of gravity is limited.

As an alternative to one of the first stop elements 341 *, which are attached to the base plate, a first stop element - in a variant, not shown - be mounted on the base plate 38 * and strike the base plate 34 * when the material thickness reaches the first thickness or exceeds.

In the Fig. 2 the deformation of a brush element Bi + 1 * is shown in comparison with a brush element Bi *. The deformation of brush elements occurs when a thicker than that in the FIG. 1 shown flat Good 4 is pressed.

That - in the FIG. 1 shown - further spring system is mounted between the base plate 38 * and the chassis 40 * and can only be effective when the pressing force above a threshold value F1opt increases, which requires a corresponding thickness of the flat material.

In front of the printing device is a lock 42 * provided with a passage opening for mailpieces, which limits the thickness of a transmitted good to a defined maximum thickness, for example, to 10 mm.

In the Fig. 3 a pressure force / thickness diagram is displayed. The increase of the illustrated curve of the pressing force F2 is m ₂ = (F1 _min - F _{2 min} ) / (d ₁ - d ₀ ) and is equal to the spring constant R2. The increase of the illustrated curve of the pressing force F3 is m ₃ = (F3 _max - F1 _opt ) / (d ₃ - d ₂ ) and is equal to the spring constant R3. In the aforementioned embodiment, F3 _min = F1 _opt = 30 N. In practice, this is achieved by the spring force of four compression springs 42 *.

Within the aforementioned pressing force / thickness diagram, a further ordinate for the pressing force F1 is shown on the right-hand edge of the picture and a further abscissa for the representation of the deformation of the brush elements is shown on the upper edge of the picture. After striking at least the first stop element 341 * is alone in the brush used in the embodiment, a deformation of the brush elements up to the value D = 3 mm possible. It can be seen that the pressing force acting on the mail item further increases non-linearly with the deformation of the brush elements.

Because, especially with thicker goods, the rise of the curve would become too steep under the effect of the pressing force F1 applied by the brush elements, the further spring system is required, which prevents the pressing force acting on the mail piece from further increasing non-linearly with the thickness of the mail piece. The other spring system acts in this sense limiting the increase in the pressure force. Without the use of the further spring system with the spring constant R3, the brush elements would be further deformed in such a case, ie d> 5 mm, so that the total pressure force acting on the mail piece further increases non-linearly. A curve corresponding to the above case was in Fig. 3 dashed lines.

The pressing force F1, with which all the brush elements act on the mail piece in the sum, would exceed the pressing force F3 of the other spring system, which can lead to irreversible deformation of brush elements. On the other hand, the pressure force F3 should increase with a defined increase, because usually the gravity effect at a higher weight, especially for large-sized mail items, such as format B4, must be compensated.

It is envisaged, on the base plate 34 * a recording medium 32 * or a bust body is mounted.

The invention is not limited to the presently explained embodiment, since obviously other other embodiments of the invention can be developed or used, which - based on the same basic idea of the invention - are encompassed by the attached claims.

Claims (6)

Pressure device with resilient elements, in particular brush elements of a brush body with which a spring system is mechanically coupled, which has a number of spring elements (37 *) which are arranged between a base plate (34 *) and a base plate (38 *), characterized in that the brush elements (B1 *, B2 *, ..., Bi *, ..., Bn *) of the pressure device are mechanically coupled to a double spring system, that the double spring system consists of the aforementioned spring system and another with the aforementioned Spring system mechanically coupled spring system, wherein the aforementioned spring system is biased at rest to a predetermined minimum pressure force F2min and in the operating state for flat goods up to a first thickness with the thickness linearly increasing pressure force F2 exerts, wherein at rest, a lower pressure force is applied, as provided by the brush elements, that at least two first stop elements (341 *) are provided, which limit the stroke of the base plate (34 *) to the base plate (38 *) in the direction of gravity, wherein after striking the stop elements (341 *), the brush elements in the sum of a minimum pressure force F1 min, which corresponds to the sum of the deformation forces D _{B of} the brush elements at rest of the Andruckvor-direction, and wherein the brush elements in the operating state for flat goods from the first thickness to a second thickness non-linearly increasing pressure force to an optimal pressure force F1opt on the Flat Good exert and that the other spring system is biased to a total of a predetermined pressing force F3min, which is equal to the optimum pressing force F1opt of the brush elements and in the operating state for flat goods from a second thickness with the thickness linearly increasing pressure force F3 exerts, for the Andruckkräfte applies: $$\mathrm{F}\mathrm{3}\mathrm{>}\mathrm{F}\mathrm{3}\min \mathrm{=}\mathrm{F}\mathrm{1}\mathrm{opt}\mathrm{>}\mathrm{F}\mathrm{1}\mathrm{>}\mathrm{F}\mathrm{1}\min \mathrm{=}\mathrm{F}\mathrm{2}\mathrm{Max}\mathrm{>}\mathrm{F}\mathrm{2}\mathrm{>}\mathrm{F}\mathrm{2}\min \mathrm{,}$$

Pressure device according to claim 1, characterized in that the stop element (341 *) mounted on the base plate (34 *) and shaped to limit the stroke so that a stop on the base plate (38 *) is achieved. Pressure device according to claim 1, characterized in that the mechanically coupled to the aforementioned spring system further spring system consists of further spring elements (42 *) which are arranged between the base plate (38 *) and a chassis (40 *). Pressure device according to claim 3, characterized in that on the chassis (40 *) arranged limiting element (41 *) limits the movement of the base plate (38 *) and thus the action of the other spring system against the direction of gravity, whereby the further spring system is biased to the predetermined pressing force F3min. Pressure device according to claim 1, characterized in that for flat goods from the first thickness of d ₁ = 2 mm, the stroke of the base plate (34 *) to the base plate (38 *) of the pressure device is limited. Pressure device according to claim 1, characterized in that on the base plate (34 *) a recording medium (32 *) or a bus body is mounted.

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