Use Of Hoekens And Pantograph Mechanisms For Carpet Scrapping Operations

For washing of carpets, scrapping is done using a wooden plank. The edge of the plank gives pressure on the carpet to remove dirt particles and water from the carpet surface. The plank follows a straight-line path on the carpet surface. In this paper Hoeken’s and Pantograph mechanisms are used to obtain a straight-line path for carpet scrapping. Hoeken’s four-bar mechanism can produce the same desired path, but the length is very small. The Pantograph mechanism is attached to magnify the length so that the scrapping length per stroke is same as that by the human operator. Combining these two mechanisms a carpet scrapping machine is developed for carpet cleaning purposes. The machine has been designed according to the force required to remove water and dirt particles from the carpet. It is driven by an electric motor and can move in any direction on the carpet. INTRODUCTION India is one of the biggest exporter of carpets in the world. Carpet processing involves several steps e.g., weaving (hand knotted), washing, drying, trimming, etc. Here the focus is carpet washing, which is done using a wooden scrapper (Fig. 1) by a human being. It is a laborious and hazardous step, as several chemicals like caustic soda, etc. are used. A carpet cleaning machine by the name “Carpet Scrapping Machine” that can perform the same job as the human washer is developed for carpet cleaning processes. For manual washing a wooden plank is used which has an extended wooden handle as shown in Fig. 1. Pressure is applied on the wet carpet through the edge of plank to remove excess wool and water from the carpet surface. The edge of plank follows a closed path containing a straight-line and a parabolic curve as shown in Fig. 2. In order to generate the path for manual scrapping, Hoeken’s four-bar mechanism is suitable [1]. However, the size of the curve is small, so to enlarge the curve size, the Pantograph mechanism [2] is introduced. Using these two mechanisms a carpet scrapping machine is realized which is driven by an electric motor. For easy movement of the machine, the wheels of the machine are also powered. PREVIOUS WORK The purpose of washing of carpet is to remove water, dust particles, excess piles and chemical from the carpet surface. It needs a massage to open the piles and to provide shininess of the carpet. For this purpose, the first machine was developed to copy the action of the human washer called washerman. The machine used slider crank mechanism where the slider was the scrapper pad. The machine hit the carpet and removed water from the carpet surface. However, the machine was drawing back some dirty water on the already cleaned surface during the return stroke. So a modification was desired to exactly copy the washerman’s action i.e. move the scrapper straight in the forward stroke and in a parabolic curve in the return stroke, as shown in Fig. 2. To copy the profile made by the edge of wooden plank the Hoeken’s mechanism [2] is proposed. This type of profile allows to throw water and dust particles in one direction and returns without touching the carpet like the washerman’s scrapper. DESIGN METHODOLOGY The aim here is to develop a compact, lightweight, easily operated, economic machine. The design involves kinematic synthesis of the mechanisms and mechanical design of the components. In this paper kinematic synthesis is presented. Fig. 1. Existing scrapper pad on carpet Plank Carpet Handle The action of the washerman during the washing of the carpet was analysed. It was found that to remove water manually a straight-line motion is followed at the bottom edge of scrapper pad. After completing a desired area the pad is lifted up and stroked again on the carpet as indicated in Fig. 2. In the beginning the scrapper pad angle is about 50.5°, which gradually decreases along with forward motion. At the end the angle is approximately 29°. Path followed by the edge of pad Fig. 2. Scrapper pad path Free body diagram of pad.