IES59854B2 - A manhole assembly - Google Patents

Description

A Learning and Teaching Aid This specification describes a learning and teaching aid and it will be described throughout the specification as the Aid. Six accompanying drawings are titled Sheet 1 to Sheet 6. Sheet 1 and Sheet 2 show perspective views of the casing of the Aid. Sheet 1 shows one side facing to the right and Sheet 2 shows the other side. The main functions of the Aid as described in this specification are to add combinations of positive whole numbers between 0 and 20 (21 numbers) on one side, and to execute corresponding subtractions on the other side. However, the capacity of the Aid is limited only by 10 physical size, and by the size of the numbers. On the addition side it also enables the student to identify and form a mental picture of each digit as representing a definite number of objects. Adaptations necessary to enable the Aid to carry out multiplication and division are also described. The numbers shown in the small windows arc carried on the mechanism underneath the windows. Knobs on both ends operate the mechanism.

Sheet 3 shows an outline plan. A, B and C arc three cylindrical drums which arc rotated inside the casing. Drums A and B are the same width, but drum C is wider. Addition is read with the wide drum on the right, and subtraction is read with the wide drum on the left. Sections on DD and EE are identical and are shown on sheet 4. Sheet 5 shows section on FF.

Sheet 4, Figure 1 shows a section on DD or on EE (see sheet 3). This drawing should be read in conjunction with Sheet 5. Line joining H to centre is centre line of windows on the addition side, and line joining J to centre is centre line of window^on subtraction side.In drum position shown O appears under windows on each side.

L is a positioning mechanism which ensures that the drum comes to rest only when there is a number directly underneath a window. It's movement is controlled by tension spring P. Sheet 4 Figure 2 shows it in more detail. Bracket M is fixed to the casing and positioning wheel N is free to turn on it's spindle. These two mechanisms (one on drum A and one on drum B) have another important function which will be described later. Reverting to Figure 1 it is necessary for the drum to have 9 location positions and two stop positions. To achieve this it is necessary to have stop pin K, and ten location pins positioned as shown.

In position shown the drum is prevented from rotating further in anticlockwise direction by stop pin K and location pin a. If rotated in clockwise direction the drum will be stopped by stop pin K and location pin β. It will have rotated through angle 20/21( 2 π). If capacity of Aid is x numbers all three drums rotate through angle 2 π · The location pins lie on circumference (c) of circle concentric with drum centre and 1/3 of its diameter (approx.). All pins are located on pin circumference (c). Pin a is located 1/21 [(c)] anti- clockwise from line joining H to centre. Pin β is located 2/21 [(c)] in clockwise direction from same line. The remaining 8 pins are spaced at equal distances around circumference (c).

Sheet 5 shows a section on FF (see sheet 3). Two only location pins are shown and the gears are not hatched, for clarity. P/^and Pg arc connected to their respective springs (see sheet 4). Rj, R2, R3 and R4 are straight bevel gears with equal PD's. Rj and R2 are free to rotate. R3 rotates with the main shaft. R4 is connected to sleeve which is in turn connected to disc of drum B. Drum A rotates with the shaft and gear R3 . Q is a subshaft and socket connected to drum C, and free to rotate on main shaft. Drums A and C are rotated by knobs on right and left respectively. A drives C and C drives B. This is made possible because reaction torque on A and B is adjustable through springs of positioning mechanisms.

This obviates the necessity of having external drive to drum B and contributes to a simple symmetrical, and economical solution. Ka and Kg are stop pins. La, Ma, Na, and Lg, Mg, Ng are parts of positioning mechanism. S and T arc collars attached to shaft, a and β are two location pins, two others only being shown.

Sheet 6 gives a perspective view of the drums, giving relative layout of numbers. Z-Zo indicates centre line of windows. The three rows of numbers on the right hand side of the drums are offset, so that 10 subtraction can be read on the other side.

To adapt the Aid as described above to read multiplication and division it is necessary only (a) to space the location pins (see sheet 4) on a logarithmic scale around circumference of pin circle, (b) To commence numbers with digit 1 and layout same on logarithmic scale on circumference of drums.

There is a feature on the Aid which is not shown on the drawings. Referring to Sheet 1 and Sheet 2 the numbers on the right (top end) can be blanked off by operating a small lever in each case, which closes a blind obstructing the view of the number. This feature enables the student to check his/her progress. Alternatively it enables the teacher to test the student.

Claims (3)

1. The Aid as described in above specification docs not form part of the state of the art.

2. This invention will help children (and adults) to learn, or be taught, 5 concept of number, addition, subtraction, multiplication, and division.

3. Operation of the gears in conjection with the spring loaded positioning mechanisms, the split shaft, and the numbering layouts, 10 are combined in such a manner as to constitute an inventive step.