DE69702701T2 - Sweeper and filter with electromagnetic filter cleaning - Google Patents

Description

FIELD OF INVENTION

The present invention relates to sweepers of the type generally shown in US-A-4,787,923, owned by Tennant Company, Minneapolis, Minn., assignees of the present application. The present invention relates in particular to an improved filter and the means for cleaning the filter.

Currently, sweepers, as shown in the above-mentioned patent 4,787,923A, place a filter in the air path of the sweepers so that dirt is trapped under the filter and clean air passes through the filter to the vacuum blower. Such filters are periodically cleaned with shaker bars, as again shown in the patent 4,787,923A. Shaker bars are not particularly effective as a cleaning device and the filter plate is often not cleaned effectively and sufficiently. In the present invention, the filter media is electromagnetically shaken by attaching one or more small transformers to the top of the filter media and then using bars or other metal elements, such as rods, to move the filter media. When voltage is applied to the transducers, the rods or metal elements move and in one form of the invention the transducers are pulsed so that the vibration of the rods and hence the folds of the filter causes the filter to be very effectively cleaned by shaking and the dirt to fall down into the dirt collecting chamber. The electromagnetic filter cleaning of the present invention is essentially noiseless, simple in construction and results in relatively little vibration of the filter medium. The entire filter plate can be cleaned or segments of the plate can be cleaned either sequentially or alternately. For example, one section of the plate can be cleaned and the other section can continue to function to direct air along the air flow path of the sweeper. In its broadest sense, the invention enables the electromagnetic cleaning of the filter of a sweeper using at least one transducer or magnetic coil.

In one form of the invention, a plurality of transducers are arranged above a filter plate consisting of generally parallel pleats. Portions of the pleats are connected in groups by a pleat block. At the top of each pleat block is an elongated metal bar. Two pleat blocks are associated with each transducer and when the transducer is pulsed, the elongated bars move toward the transducer. The resulting reciprocating motion of the elongated bars and the resulting movement of the pleat blocks and pleats causes the pleats to shake considerably, thereby dislodging the dirt that has become baked on and trapped therein.

Preferably, the transducers are not operated simultaneously but in a predetermined sequence. This reduces the power consumption of a machine that is often battery-operated. One or more transducers can be pulsed at any time, and the transducers are pulsed in a predetermined sequence so that the entire pleated filter is cleaned over a short period of time. The duration of the pulsed voltage can be controlled as well as the frequency of the pulsed voltage and the intervals between the pulsed voltage applications.

The action of the pulsed voltage, by which the pleat blocks are drawn towards the transducer, causes the pleats in adjacent pleat blocks to move towards each other and at least partially come into contact with each other, thereby amplifying the vibration acting on the individual pleats, which contributes to the loosening of dirt and baked-on residues from the pleated filter element.

SUMMARY OF THE INVENTION

The present invention relates to sweeping machines and, in particular, to an electromagnetic filter cleaning device for sweeping machines.

A main purpose of the invention is a filter cleaning device for the described purpose according to the features of claims 1, 18 and 35. Ultrasonic transducers arranged above the pleated filter can be used, with the filter pleats connected to metal elements which are moved by the pulsed energy so that the pleats are shaken for cleaning.

Preferably, a further purpose in a filter cleaning system as described, in which the sequence of actuation of the transducers is controlled, is to reduce power consumption.

Preferably, a further purpose in a filter cleaning system as described, in which the duration and frequency of operation of the transducers is controlled, is to maximize the cleaning of the filters.

Other purposes of embodiments of the invention will become apparent from the specification, drawings and dependent claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are shown schematically in the following drawings, wherein:

Fig. 1 is a schematic representation of a sweeper of the type employing the cleaning system disclosed herein;

Fig. 2 is a plan view of the filter element showing the electromagnetic agitators attached thereto;

Fig. 3 is a section along the plane 3-3 in Fig. 2;

Fig. 4 is a side view of a pleat block;

Fig. 5 is a plan view of a pleat block;

Fig. 6 is a partial plan view of a modified form of electromagnetic shaking system;

Fig. 7 is a section along the line 7-7 in Fig. 6;

Fig. 8 is a side view of the fold block of the embodiment in Figs. 6 and 7;

Fig. 9 is a plan view of the pleat block in Fig. 8;

Fig. 10 is a plan view of a modified form of the pleat block;

Fig. 11 is a side view of the fold block in Fig. 10; and

Fig. 12 is an electrical diagram of the control system for the electromagnetic shakers shown here.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In Fig. 1, a typical street sweeper 10 is shown. The sweeper 10 has a brush 12 which directs dirt and debris into a container 14. Wheels 16 support the sweeper 10. There is a vacuum fan 18 which creates an air flow path in the direction of arrows 20. In the air flow path is a filter 22 which is shown in detail in the following figures.

The filter 22, as particularly shown in Figures 2 to 5, includes a peripheral frame 24 that includes side walls 26. Within the side walls 26 is a pleated filter element 28 that includes upper pleats 30 and lower pleats 32. The filter element may be of conventional type and may be made of paper or plastic materials depending on the requirements of the application. The top of the filter 22 includes a screen cover 34 made of aluminum.

Mounted above the filter 22 is a transducer assembly which includes a support bar 36 on which a plurality of transducers or electrical coils 38 are mounted. The ends of the support bar 36 may be supported by brackets 40, as particularly shown in Fig. 3.

There are five transducers, as shown in Fig. 2, which may be sufficient for a filter panel of 20 x 30 inches. The number of transducers is not critical and can be determined by the size of the panel. Four transducers may also be sufficient for the same panel size, and the number of transducers is determined in part by the voltage and frequency at which the transducers are operated.

The folds 38 may be partially divided into groups as shown in Figure 3 and connected by fold blocks 42. The fold blocks 42, which may be made of a suitable plastic and have the external shape of a comb, have a top surface 44 and a plurality of downwardly extending projections 46 extending between adjacent folds, the upper folds 30 of the folds in a group being connected by a fold block extending into the space between the projections 46. There are two groups of folds connected by fold blocks arranged adjacent to the transducer 38. The adjacent fold blocks are arranged with a small spacing directly below the coil of the transducer. An elongated metal strip 48 is recessed into the top surface of each fold block 42, the strips extending over a substantial part of the width of the fold block, although this is not necessary. By dividing the pleats into groups and arranging the groups so that they are functionally close to the transducer, an arrangement of pleat blocks is created with the most effective means of removing dirt and caked-on dust from the pleats.

When each of the transducers is activated by a pulse of electrical voltage, an electromagnetic field is created around it. The field attracts the elongated strips 48 toward the center of the transducer. Such movement of the strips creates a simultaneous movement of the pleat blocks, causing the pleats connected by the pleat block to move simultaneously therewith. Reciprocation of the adjacent pleat blocks not only causes the pleats to vibrate, but also causes the pleat blocks to come into contact with one another, further jostling and shaking the pleats. Since the transducers are advantageously pulsed and voltage is not continuously applied with each pulse acting on the transducer, the pleat blocks connected to that transducer move toward one another, and when the voltage is turned off, the pleat blocks return to their rest position shown in Fig. 3 due to the inherent elasticity of the pleats. Therefore, the application of the pulsed voltage causes the pleat blocks and the pleats connected by the pleat blocks to oscillate. This rapid oscillation, which occurs at intervals determined by the control circuit described below, causes the pleat blocks to shake or oscillate, causing the pleats to move at high speed so that the dirt accumulated in the pleats is shaken off and falls into the dirt collection chamber directly below the filter.

The embodiment of the invention shown in Figs. 2-5 employs elongated strips extending transversely to the direction of the folds and responsive to the electromagnetic fields generated by the voltage pulses applied to the transducers. The embodiment of the invention shown in Figs. 6-9 also employs elongated metal elements, but in a different orientation. As shown particularly in Figs. 6-7, an elongated rod or wire 50 is enclosed in the upper fold 30 of one of the folds, which are connected together by the fold block 52. The rod or wire 50 extends substantially the entire length of the folds, as shown in Fig. 6. The wires or rods are made of metal and are responsive to an electromagnetic field generated by the pulsed voltage applied to the transducer. Again, two groups of folds belong to each transducer, and a single elongated element is located in each fold block.

In the embodiment of Fig. 6-9, the rods extend parallel to the folds and are moved by the action of an electromagnetic field from the transducer. The rods move toward the center of the transducer and in doing so move the fold blocks back and forth in the same way as the fold blocks in the embodiment of Fig. 2-5. The fold blocks shown in Figs. 8 and 9 are essentially the same as blocks 4-5, but do not have an elongated metal strip included in their surface. Again, the movement of the fold blocks is due to the use of elongated rods which move toward the center line of the transducer when pulsed voltage is applied to them. The movement of the fold blocks is essentially the same in both embodiments.

A modified form of pleat block is shown in Figs. 10 and 11. In this case, the pleat block, generally indicated at 60, has a comb 62, in the surface of which a metal strip 64 is embedded. In this respect, it is similar to the pleat block shown in Figs. 4 and 5. Connected to the comb 62 is an elongated support 66 which has downwardly projecting projections 68 as shown in Fig. 11 and which rests on two adjacent pleats. Thus, reciprocating movement of the pleat block towards and away from the transducer, as described in connection with the embodiment in Figs. 2 to 5, now results in transverse movement over the entire length of the pleats in the group. There is no longer any dependence on the movement of the comb alone, which has a limited width, but the carrier 6b ensures that the movement acting on the folds extends over the entire length of the folds in the group.

Fig. 12 shows the control circuit for all the embodiments already described. The transducer coils are shown at 70 and labeled as coils 1 to 5. The number of coils can again vary and is not critical to the invention. There are a number of amplifiers 72, with one amplifier for each coil. The amplifiers are connected to a sequencer 74, the sequencer being controlled by a clock 76. The clock 76 and the sequencer 74 determine which coils are operated and in what sequence. For example, it may be advantageous to operate a single transducer or coil at a time, with the coils being energized in a specific sequence depending on their arrangement over the filter element in order to achieve the most effective cleaning. It is also within the scope of the invention to operate more than one transducer at the same time. For example, two coils may be energized at once, or the coils may be energized such that a single coil is energized and before that is turned off, a second coil is energized and a third coil is energized before the second coil is turned off. Any sequence is within the scope of the invention. It is important that the voltage is applied in the form of pulses and that not all coils are energized at the same time to avoid excessive current consumption of the sweeper's power supply, which is traditionally a battery.

Identified at 78 is a second clock, designated clock number 1, which determines the duration of the pulses applied. This clock is activated by the operator via the remote shake button and initiates a cleaning operation. The output of clock number 1, designated at 78, is a series of pulses, the clock controlling the period of the pulses and thus the time between successive pulses. This series of pulses goes to an intensity generator 80 which has a remote intensity control and a remote frequency control. The output from the intensity generator is a series of pulses having a frequency and an intensity determined by the operator. The intensity or amplitude of the pulses controls the electromagnetic field generated by each transducer. The pulses from intensity generator 80 are applied to amplifiers 72, designated amplifiers A through E. There is one amplifier for each coil. The circuit shown applies pulses of a desired frequency and amplitude, as well as a predetermined duration between pulses, to the amplifiers, which in turn are activated in the desired sequence by clock number 2 to control the voltage applied to coils 70.

It has been found that a frequency of 30 Hz when applying the pulses provides effective cleaning. The sequencing can be set to allow two seconds for each cleaning segment, whether a single transducer or more than one transducer is involved. The cleaning cycle is effectively carried out with the transducers energized 30% of the time and de-energized 70% of the time. Although the invention should not be limited to the specific parameters, it has been found that effective cleaning can be achieved with these.

Although the preferred form of the invention has been shown and described, it is obvious that many modifications, substitutions and alternatives are possible as defined in the claims.

Claims (35)

1. A sweeping machine (10) comprising a housing, wheels (16) for moving the housing, a sweeping brush (12) attached to the housing, a container (14) positioned adjacent the brush (12) for collecting dirt and debris therefrom, a dirt collection chamber on the housing, a vacuum fan (18) attached to the housing and creating an air flow path from the brush (12) through the container (14) and to the dirt collection chamber, and a filter element (22) in the air flow path, the filter element (22) including a plurality of generally parallel pleats (28) extending in a direction transverse to the air flow path, characterized by a plurality of electrical coils (38) positioned adjacent the pleats, a plurality of metal elements (48) associated with the pleats, and means for applying pulsed electrical energy to the electrical Coils (38), the electromagnetic fields generated thereby moving the metal elements (48) and the associated folds to cause the folds (28) to undergo a shaking cleaning motion. 2. A sweeper according to claim 1, wherein at least some of the filter pleats are divided into groups and each group includes an electrical coil. 3. A sweeper according to claim 2, which includes a device for connecting the folds in a group. 4. A sweeper according to claim 3, wherein the means for connecting folds in a group carries one of the plurality of metal elements. 5. A sweeper according to claim 4, wherein the folds have upper and lower folds and the means for connecting the folds in a group engages the upper folds of the folds in a group. 6. A sweeper according to claim 5, wherein the means for connecting a group of pleats includes a comb having a top and downwardly projecting comb elements, the comb elements each being arranged between adjacent folds. 7. A sweeper according to claim 5, wherein each of the metal elements extends in a direction transverse to the fold folds. 8. A sweeper according to claim 7, wherein the metal elements move towards and away from the coils when pulsed electrical energy is applied to the coils to produce movement of the folds in a group associated with a particular metal element. 9. A sweeper according to claim 2, wherein two groups of pleats are associated with each coil, i.e. one group on each side of the coil, and upon application of pulsed energy the groups of pleats are moved towards each other. 10. A sweeper according to claim 2, including means for connecting folds in a group, the means including a first member seated on upper folds of folds in a group and extending transversely to the upper folds, and a second member attached to the first member and extending parallel to the upper folds of folds in a group, each of the first members carrying one of the plurality of metal members. 11. A sweeper according to claim 2, wherein the folds each have spaced parallel upper and lower folds, elongated wire elements associated with certain ones of the upper folds of the folds, the wire elements being moved and causing movement of folds in a group in response to the application of pulsed electrical energy to the coils. 12. A sweeper according to claim 11, wherein the elongated wires are made of metal and represent the metal elements connected to the folds. 13. The sweeper of claim 1, wherein the means for applying pulsed electrical energy to the coil includes means for limiting simultaneous application of energy to less than all of the coils. 14. A sweeper according to claim 13, wherein the means for applying pulsed electrical energy includes circuit means for applying energy to the coils in a predetermined sequence. 15. A sweeper according to claim 14, wherein the means for applying pulsed electrical energy includes circuit means for limiting the application of pulsed electrical energy to each coil to a predetermined period of time. 16. A sweeper according to claim 13, wherein the means for applying pulsed electrical energy includes means for varying the intensity of the applied energy. 17. A sweeper according to claim 13, wherein the means for applying pulsed electrical energy includes means for varying the frequency of the applied energy. 18. A pleated air filter (22) and means for cleaning the same, the filter including a frame (36) and a plurality of generally parallel pleats (28) mounted in the frame, the pleats each having spaced parallel upper (30) and lower (32) folds, characterized by an elongated metal member (48) associated with certain ones of the upper folds of the pleats, at least one electrical coil (38) mounted on the frame above the upper folds of the pleats, means for applying pulsed electrical energy to the at least one coil (38) so as to generate an electromagnetic field, the pulsed electromagnetic field having back and forth Movement of the metal element (48) in a direction transverse to the generally parallel folds (28) to impart a shaking cleaning motion to the folds (28). 19. A filter according to claim 18, wherein the elongated metal element extends parallel to the upper folds of the pleat. 20. The filter of claim 19, wherein the elongated metal member is a wire attached to an upper fold of the pleats. 21. A filter according to claim 18, wherein the elongated metal element extends transversely to the upper folds of the pleats and is moved toward and away from the electrical coil by the pulsed electrical energy applied to the electrical coil. 22 A filter according to claim 18, wherein the pleats are divided into groups and each group of pleats includes a coil. 23. A filter according to claim 22, wherein at least a portion of the pleats in each group are interconnected at upper pleats thereof by a pleat block, and movement of an elongate metal member in a direction transverse to the generally parallel pleats causes movement of the associated pleat block and the pleats connected thereto. 24. A filter according to claim 23, wherein an elongated metal element is associated with each pleat block. 25. The filter of claim 23, wherein there are a plurality of electrical coils, and each coil includes two pleat blocks, and the pleat blocks are disposed generally on either side of the center of the coil. 26. A filter according to claim 25, wherein each pleat block includes an elongated metal element. 27. The filter of claim 26, wherein the elongated metal elements are attached to the top of a pleat block and extend in a direction transverse to the generally parallel pleats. 28. The filter of claim 23, wherein the pleat blocks extend in a direction transverse to the generally parallel pleats. 29. The filter of claim 28, wherein each pleat block includes a portion extending generally parallel to and at the top of the generally parallel pleats. 30. The filter of claim 18, wherein there are a plurality of electrical coils, and wherein the means for applying pulsed electrical energy to the coils includes means for limiting the simultaneous application of energy to less than all of the coils. 31. A filter according to claim 30, wherein the means for applying pulsed electrical energy includes circuit means for applying energy to the coils in a predetermined sequence. 32. A filter according to claim 30, wherein the means for applying energy includes circuitry means for limiting the application of pulsed electrical energy to each coil to a predetermined period of time. 33. The filter of claim 30, wherein the means for applying pulsed electrical energy includes means for varying the intensity of the applied pulsed energy. 34. A filter according to claim 30, wherein the means for applying energy includes circuitry means for varying the frequency of the applied energy. 35. Sweeping machine (10) comprising a housing, wheels (16) for moving the housing, a sweeping brush (12) attached to the housing, a container (14), disposed adjacent to the brush (12) to collect dirt and debris therefrom, a dirt collection chamber on the housing, a vacuum fan (18) attached to the housing and creating an airflow path from the brush (12) through the container (14) and to the dirt collection chamber, and a filter element (22) in the airflow path, the filter element (22) including a plurality of generally parallel pleats (28) extending in a direction transverse to the airflow path, characterized by at least one electrical coil (38) disposed adjacent to the pleats, at least one metal element (48) associated with the pleats, and means for applying electrical energy to the at least one coil (38), the electromagnetic field generated thereby moving the at least one metal element (48) and the associated pleats (28) to impart an agitating cleaning motion to the pleats (28).